Let's add a few pr_info's to sev_hardware_setup to make SEV/SEV-ES
enabling a little bit handier for users. Right now it's too hard
to guess why SEV/SEV-ES are failing to enable.
There are a few reasons.
SEV:
- npt is disabled (module parameter)
- CPU lacks some features (sev, decodeassists)
- Maximum SEV ASID is 0
SEV-ES:
- mmio_caching is disabled (module parameter)
- CPU lacks sev_es feature
- Minimum SEV ASID value is 1 (can be adjusted in BIOS/UEFI)
Cc: Sean Christopherson <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Stéphane Graber <[email protected]>
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Alexander Mikhalitsyn <[email protected]>
---
arch/x86/kvm/svm/sev.c | 27 +++++++++++++++++++++------
1 file changed, 21 insertions(+), 6 deletions(-)
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index a42536a0681a..14cbb8f14c6b 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -2168,17 +2168,24 @@ void __init sev_hardware_setup(void)
bool sev_es_supported = false;
bool sev_supported = false;
- if (!sev_enabled || !npt_enabled)
+ if (!sev_enabled)
goto out;
+ if (!npt_enabled) {
+ pr_info("Failed to enable AMD SEV as it requires Nested Paging to be enabled\n");
+ goto out;
+ }
+
/*
* SEV must obviously be supported in hardware. Sanity check that the
* CPU supports decode assists, which is mandatory for SEV guests to
* support instruction emulation.
*/
if (!boot_cpu_has(X86_FEATURE_SEV) ||
- WARN_ON_ONCE(!boot_cpu_has(X86_FEATURE_DECODEASSISTS)))
+ WARN_ON_ONCE(!boot_cpu_has(X86_FEATURE_DECODEASSISTS))) {
+ pr_info("Failed to enable AMD SEV as it requires decodeassists and sev CPU features\n");
goto out;
+ }
/* Retrieve SEV CPUID information */
cpuid(0x8000001f, &eax, &ebx, &ecx, &edx);
@@ -2188,8 +2195,10 @@ void __init sev_hardware_setup(void)
/* Maximum number of encrypted guests supported simultaneously */
max_sev_asid = ecx;
- if (!max_sev_asid)
+ if (!max_sev_asid) {
+ pr_info("Failed to enable SEV as the maximum SEV ASID value is 0.\n");
goto out;
+ }
/* Minimum ASID value that should be used for SEV guest */
min_sev_asid = edx;
@@ -2234,16 +2243,22 @@ void __init sev_hardware_setup(void)
* instead relies on #NPF(RSVD) being reflected into the guest as #VC
* (the guest can then do a #VMGEXIT to request MMIO emulation).
*/
- if (!enable_mmio_caching)
+ if (!enable_mmio_caching) {
+ pr_info("Failed to enable SEV-ES as it requires MMIO caching to be enabled\n");
goto out;
+ }
/* Does the CPU support SEV-ES? */
- if (!boot_cpu_has(X86_FEATURE_SEV_ES))
+ if (!boot_cpu_has(X86_FEATURE_SEV_ES)) {
+ pr_info("Failed to enable SEV-ES as it requires sev_es CPU feature\n");
goto out;
+ }
/* Has the system been allocated ASIDs for SEV-ES? */
- if (min_sev_asid == 1)
+ if (min_sev_asid == 1) {
+ pr_info("Failed to enable SEV-ES as the minimum SEV ASID value is 1.\n");
goto out;
+ }
sev_es_asid_count = min_sev_asid - 1;
if (misc_cg_set_capacity(MISC_CG_RES_SEV_ES, sev_es_asid_count))
--
2.34.1
On Tue, 4 Apr 2023 14:26:52 +0200
Alexander Mikhalitsyn <[email protected]> wrote:
> Let's add a few pr_info's to sev_hardware_setup to make SEV/SEV-ES
> enabling a little bit handier for users. Right now it's too hard
> to guess why SEV/SEV-ES are failing to enable.
>
> There are a few reasons.
> SEV:
> - npt is disabled (module parameter)
^NPT
> - CPU lacks some features (sev, decodeassists)
> - Maximum SEV ASID is 0
>
> SEV-ES:
> - mmio_caching is disabled (module parameter)
> - CPU lacks sev_es feature
> - Minimum SEV ASID value is 1 (can be adjusted in BIOS/UEFI)
>
> Cc: Sean Christopherson <[email protected]>
> Cc: Paolo Bonzini <[email protected]>
> Cc: St?phane Graber <[email protected]>
> Cc: [email protected]
> Cc: [email protected]
> Signed-off-by: Alexander Mikhalitsyn <[email protected]>
> ---
> arch/x86/kvm/svm/sev.c | 27 +++++++++++++++++++++------
> 1 file changed, 21 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index a42536a0681a..14cbb8f14c6b 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -2168,17 +2168,24 @@ void __init sev_hardware_setup(void)
> bool sev_es_supported = false;
> bool sev_supported = false;
>
> - if (!sev_enabled || !npt_enabled)
> + if (!sev_enabled)
> goto out;
>
> + if (!npt_enabled) {
> + pr_info("Failed to enable AMD SEV as it requires Nested Paging to be enabled\n");
> + goto out;
Shouldn't we use pr_err() for error message?
> + }
> +
> /*
> * SEV must obviously be supported in hardware. Sanity check that the
> * CPU supports decode assists, which is mandatory for SEV guests to
> * support instruction emulation.
> */
> if (!boot_cpu_has(X86_FEATURE_SEV) ||
> - WARN_ON_ONCE(!boot_cpu_has(X86_FEATURE_DECODEASSISTS)))
> + WARN_ON_ONCE(!boot_cpu_has(X86_FEATURE_DECODEASSISTS))) {
> + pr_info("Failed to enable AMD SEV as it requires decodeassists and sev CPU features\n");
> goto out;
> + }
>
> /* Retrieve SEV CPUID information */
> cpuid(0x8000001f, &eax, &ebx, &ecx, &edx);
> @@ -2188,8 +2195,10 @@ void __init sev_hardware_setup(void)
>
> /* Maximum number of encrypted guests supported simultaneously */
> max_sev_asid = ecx;
> - if (!max_sev_asid)
> + if (!max_sev_asid) {
> + pr_info("Failed to enable SEV as the maximum SEV ASID value is 0.\n");
> goto out;
> + }
>
> /* Minimum ASID value that should be used for SEV guest */
> min_sev_asid = edx;
> @@ -2234,16 +2243,22 @@ void __init sev_hardware_setup(void)
> * instead relies on #NPF(RSVD) being reflected into the guest as #VC
> * (the guest can then do a #VMGEXIT to request MMIO emulation).
> */
> - if (!enable_mmio_caching)
> + if (!enable_mmio_caching) {
> + pr_info("Failed to enable SEV-ES as it requires MMIO caching to be enabled\n");
> goto out;
> + }
>
> /* Does the CPU support SEV-ES? */
> - if (!boot_cpu_has(X86_FEATURE_SEV_ES))
> + if (!boot_cpu_has(X86_FEATURE_SEV_ES)) {
> + pr_info("Failed to enable SEV-ES as it requires sev_es CPU feature\n");
> goto out;
> + }
>
> /* Has the system been allocated ASIDs for SEV-ES? */
> - if (min_sev_asid == 1)
> + if (min_sev_asid == 1) {
> + pr_info("Failed to enable SEV-ES as the minimum SEV ASID value is 1.\n");
> goto out;
> + }
>
> sev_es_asid_count = min_sev_asid - 1;
> if (misc_cg_set_capacity(MISC_CG_RES_SEV_ES, sev_es_asid_count))
As this patch is making sev_hardware_setup()more informative, it would be
better to print both ASID range and count (instead of only ASID count in
the current code). I was suspecting there seems a bug of ASID range allocation
in the current code, but I don't have the HW to test yet...
On Tue, Apr 11, 2023 at 9:43 PM Zhi Wang <[email protected]> wrote:
>
> On Tue, 4 Apr 2023 14:26:52 +0200
> Alexander Mikhalitsyn <[email protected]> wrote:
>
> > Let's add a few pr_info's to sev_hardware_setup to make SEV/SEV-ES
> > enabling a little bit handier for users. Right now it's too hard
> > to guess why SEV/SEV-ES are failing to enable.
> >
> > There are a few reasons.
> > SEV:
> > - npt is disabled (module parameter)
> ^NPT
> > - CPU lacks some features (sev, decodeassists)
> > - Maximum SEV ASID is 0
> >
> > SEV-ES:
> > - mmio_caching is disabled (module parameter)
> > - CPU lacks sev_es feature
> > - Minimum SEV ASID value is 1 (can be adjusted in BIOS/UEFI)
> >
> > Cc: Sean Christopherson <[email protected]>
> > Cc: Paolo Bonzini <[email protected]>
> > Cc: Stéphane Graber <[email protected]>
> > Cc: [email protected]
> > Cc: [email protected]
> > Signed-off-by: Alexander Mikhalitsyn <[email protected]>
> > ---
> > arch/x86/kvm/svm/sev.c | 27 +++++++++++++++++++++------
> > 1 file changed, 21 insertions(+), 6 deletions(-)
> >
> > diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> > index a42536a0681a..14cbb8f14c6b 100644
> > --- a/arch/x86/kvm/svm/sev.c
> > +++ b/arch/x86/kvm/svm/sev.c
> > @@ -2168,17 +2168,24 @@ void __init sev_hardware_setup(void)
> > bool sev_es_supported = false;
> > bool sev_supported = false;
> >
> > - if (!sev_enabled || !npt_enabled)
> > + if (!sev_enabled)
> > goto out;
> >
> > + if (!npt_enabled) {
> > + pr_info("Failed to enable AMD SEV as it requires Nested Paging to be enabled\n");
> > + goto out;
>
> Shouldn't we use pr_err() for error message?
I'm not sure. Because technically that's not an error, that is an
information message about current configuration.
>
> > + }
> > +
> > /*
> > * SEV must obviously be supported in hardware. Sanity check that the
> > * CPU supports decode assists, which is mandatory for SEV guests to
> > * support instruction emulation.
> > */
> > if (!boot_cpu_has(X86_FEATURE_SEV) ||
> > - WARN_ON_ONCE(!boot_cpu_has(X86_FEATURE_DECODEASSISTS)))
> > + WARN_ON_ONCE(!boot_cpu_has(X86_FEATURE_DECODEASSISTS))) {
> > + pr_info("Failed to enable AMD SEV as it requires decodeassists and sev CPU features\n");
> > goto out;
> > + }
> >
> > /* Retrieve SEV CPUID information */
> > cpuid(0x8000001f, &eax, &ebx, &ecx, &edx);
> > @@ -2188,8 +2195,10 @@ void __init sev_hardware_setup(void)
> >
> > /* Maximum number of encrypted guests supported simultaneously */
> > max_sev_asid = ecx;
> > - if (!max_sev_asid)
> > + if (!max_sev_asid) {
> > + pr_info("Failed to enable SEV as the maximum SEV ASID value is 0.\n");
> > goto out;
> > + }
> >
> > /* Minimum ASID value that should be used for SEV guest */
> > min_sev_asid = edx;
> > @@ -2234,16 +2243,22 @@ void __init sev_hardware_setup(void)
> > * instead relies on #NPF(RSVD) being reflected into the guest as #VC
> > * (the guest can then do a #VMGEXIT to request MMIO emulation).
> > */
> > - if (!enable_mmio_caching)
> > + if (!enable_mmio_caching) {
> > + pr_info("Failed to enable SEV-ES as it requires MMIO caching to be enabled\n");
> > goto out;
> > + }
> >
> > /* Does the CPU support SEV-ES? */
> > - if (!boot_cpu_has(X86_FEATURE_SEV_ES))
> > + if (!boot_cpu_has(X86_FEATURE_SEV_ES)) {
> > + pr_info("Failed to enable SEV-ES as it requires sev_es CPU feature\n");
> > goto out;
> > + }
> >
> > /* Has the system been allocated ASIDs for SEV-ES? */
> > - if (min_sev_asid == 1)
> > + if (min_sev_asid == 1) {
> > + pr_info("Failed to enable SEV-ES as the minimum SEV ASID value is 1.\n");
> > goto out;
> > + }
> >
> > sev_es_asid_count = min_sev_asid - 1;
> > if (misc_cg_set_capacity(MISC_CG_RES_SEV_ES, sev_es_asid_count))
>
> As this patch is making sev_hardware_setup()more informative, it would be
> better to print both ASID range and count (instead of only ASID count in
> the current code). I was suspecting there seems a bug of ASID range allocation
> in the current code, but I don't have the HW to test yet...
On Tue, Apr 04, 2023, Alexander Miqqqqkhalitsyn wrote:
> Let's add a few pr_info's to sev_hardware_setup to make SEV/SEV-ES
> enabling a little bit handier for users. Right now it's too hard
> to guess why SEV/SEV-ES are failing to enable.
Hmm, I'm somewhat torn, but I'm against taking this patch, at least not in its
current form. I appreciated that determining why KVM isn't enabling SEV/SEV-ES
is annoying, but there's very little actionable information provided here that
isn't also super obvious. I also don't want to start us down a slippery slope
of printing out messages every time KVM doesn't enable a feature.
If someone tries to enable SEV and doesn't check that their CPU supports SEV,
then IMO that's on them. Ditto for SEV-ES.
The NPT thing is mildly interesting, but practically speaking I don't expect that
to ever be a hindrace for generic enabling. Ditto for MMIO caching.
The decode assists check is (a) completely unactionable for the vast, vast majority
of users and (b) is a WARN_ON_ONCE() condition.
The ASID stuff is by far the most interesting, but that's also quite interesting
for when SEV and SEV-ES _are_ fully supported.
So if we want to provide the user more info, I'd prefer to do something like the
below, which I think would be more helpful and would avoid my slippery slope
concerns.
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index c25aeb550cd9..eb4c6e3812d9 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -2216,7 +2216,6 @@ void __init sev_hardware_setup(void)
if (misc_cg_set_capacity(MISC_CG_RES_SEV, sev_asid_count))
goto out;
- pr_info("SEV supported: %u ASIDs\n", sev_asid_count);
sev_supported = true;
/* SEV-ES support requested? */
@@ -2243,11 +2242,16 @@ void __init sev_hardware_setup(void)
sev_es_asid_count = min_sev_asid - 1;
if (misc_cg_set_capacity(MISC_CG_RES_SEV_ES, sev_es_asid_count))
goto out;
-
- pr_info("SEV-ES supported: %u ASIDs\n", sev_es_asid_count);
sev_es_supported = true;
out:
+ if (boot_cpu_has(X86_FEATURE_SEV))
+ pr_info("SEV %s (ASIDs %u - %u)\n",
+ sev_supported ? "enabled" : "disabled", ...);
+ if (boot_cpu_has(X86_FEATURE_SEV_ES))
+ pr_info("SEV-ES %s (ASIDs %u - %u)\n",
+ sev_es_supported ? "enabled" : "disabled", ...);
+
sev_enabled = sev_supported;
sev_es_enabled = sev_es_supported;
#endif
On Fri, May 19, 2023 at 8:17 PM Sean Christopherson <[email protected]> wrote:
>
> On Tue, Apr 04, 2023, Alexander Miqqqqkhalitsyn wrote:
> > Let's add a few pr_info's to sev_hardware_setup to make SEV/SEV-ES
> > enabling a little bit handier for users. Right now it's too hard
> > to guess why SEV/SEV-ES are failing to enable.
>
> Hmm, I'm somewhat torn, but I'm against taking this patch, at least not in its
> current form. I appreciated that determining why KVM isn't enabling SEV/SEV-ES
> is annoying, but there's very little actionable information provided here that
> isn't also super obvious. I also don't want to start us down a slippery slope
> of printing out messages every time KVM doesn't enable a feature.
>
> If someone tries to enable SEV and doesn't check that their CPU supports SEV,
> then IMO that's on them. Ditto for SEV-ES.
>
> The NPT thing is mildly interesting, but practically speaking I don't expect that
> to ever be a hindrace for generic enabling. Ditto for MMIO caching.
>
> The decode assists check is (a) completely unactionable for the vast, vast majority
> of users and (b) is a WARN_ON_ONCE() condition.
>
> The ASID stuff is by far the most interesting, but that's also quite interesting
> for when SEV and SEV-ES _are_ fully supported.
>
> So if we want to provide the user more info, I'd prefer to do something like the
> below, which I think would be more helpful and would avoid my slippery slope
> concerns.
Dear Sean,
Thanks for looking into this!
I agree with your points, let's go that way and print only ASID stuff
as it can be not obvious to the end-user.
I'm ready to prepare -v2 if you don't mind.
Kind regards,
Alex
>
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index c25aeb550cd9..eb4c6e3812d9 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -2216,7 +2216,6 @@ void __init sev_hardware_setup(void)
> if (misc_cg_set_capacity(MISC_CG_RES_SEV, sev_asid_count))
> goto out;
>
> - pr_info("SEV supported: %u ASIDs\n", sev_asid_count);
> sev_supported = true;
>
> /* SEV-ES support requested? */
> @@ -2243,11 +2242,16 @@ void __init sev_hardware_setup(void)
> sev_es_asid_count = min_sev_asid - 1;
> if (misc_cg_set_capacity(MISC_CG_RES_SEV_ES, sev_es_asid_count))
> goto out;
> -
> - pr_info("SEV-ES supported: %u ASIDs\n", sev_es_asid_count);
> sev_es_supported = true;
>
> out:
> + if (boot_cpu_has(X86_FEATURE_SEV))
> + pr_info("SEV %s (ASIDs %u - %u)\n",
> + sev_supported ? "enabled" : "disabled", ...);
> + if (boot_cpu_has(X86_FEATURE_SEV_ES))
> + pr_info("SEV-ES %s (ASIDs %u - %u)\n",
> + sev_es_supported ? "enabled" : "disabled", ...);
> +
> sev_enabled = sev_supported;
> sev_es_enabled = sev_es_supported;
> #endif
On Fri, May 19, 2023, Aleksandr Mikhalitsyn wrote:
> On Fri, May 19, 2023 at 8:17 PM Sean Christopherson <[email protected]> wrote:
> >
> > On Tue, Apr 04, 2023, Alexander Miqqqqkhalitsyn wrote:
> > > Let's add a few pr_info's to sev_hardware_setup to make SEV/SEV-ES
> > > enabling a little bit handier for users. Right now it's too hard
> > > to guess why SEV/SEV-ES are failing to enable.
> >
> > Hmm, I'm somewhat torn, but I'm against taking this patch, at least not in its
> > current form. I appreciated that determining why KVM isn't enabling SEV/SEV-ES
> > is annoying, but there's very little actionable information provided here that
> > isn't also super obvious. I also don't want to start us down a slippery slope
> > of printing out messages every time KVM doesn't enable a feature.
> >
> > If someone tries to enable SEV and doesn't check that their CPU supports SEV,
> > then IMO that's on them. Ditto for SEV-ES.
> >
> > The NPT thing is mildly interesting, but practically speaking I don't expect that
> > to ever be a hindrace for generic enabling. Ditto for MMIO caching.
> >
> > The decode assists check is (a) completely unactionable for the vast, vast majority
> > of users and (b) is a WARN_ON_ONCE() condition.
> >
> > The ASID stuff is by far the most interesting, but that's also quite interesting
> > for when SEV and SEV-ES _are_ fully supported.
> >
> > So if we want to provide the user more info, I'd prefer to do something like the
> > below, which I think would be more helpful and would avoid my slippery slope
> > concerns.
>
> Dear Sean,
>
> Thanks for looking into this!
>
> I agree with your points, let's go that way and print only ASID stuff
> as it can be not obvious to the end-user.
>
> I'm ready to prepare -v2 if you don't mind.
Ya, fire away. Thanks!