From: David Stevens <[email protected]>
Migrate from __gfn_to_pfn_memslot to __kvm_follow_pfn.
Signed-off-by: David Stevens <[email protected]>
---
arch/x86/kvm/mmu/mmu.c | 35 +++++++++++++++++++++++++----------
1 file changed, 25 insertions(+), 10 deletions(-)
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index ec169f5c7dce..e44ab512c3a1 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4296,7 +4296,12 @@ void kvm_arch_async_page_ready(struct kvm_vcpu *vcpu, struct kvm_async_pf *work)
static int __kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
{
struct kvm_memory_slot *slot = fault->slot;
- bool async;
+ struct kvm_follow_pfn foll = {
+ .slot = slot,
+ .gfn = fault->gfn,
+ .flags = FOLL_GET | (fault->write ? FOLL_WRITE : 0),
+ .allow_write_mapping = true,
+ };
/*
* Retry the page fault if the gfn hit a memslot that is being deleted
@@ -4325,12 +4330,14 @@ static int __kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault
return RET_PF_EMULATE;
}
- async = false;
- fault->pfn = __gfn_to_pfn_memslot(slot, fault->gfn, false, false, &async,
- fault->write, &fault->map_writable,
- &fault->hva);
- if (!async)
- return RET_PF_CONTINUE; /* *pfn has correct page already */
+ foll.flags |= FOLL_NOWAIT;
+ fault->pfn = __kvm_follow_pfn(&foll);
+
+ if (!is_error_noslot_pfn(fault->pfn))
+ goto success;
+
+ if (fault->pfn != KVM_PFN_ERR_NEEDS_IO)
+ return RET_PF_CONTINUE;
if (!fault->prefetch && kvm_can_do_async_pf(vcpu)) {
trace_kvm_try_async_get_page(fault->addr, fault->gfn);
@@ -4348,9 +4355,17 @@ static int __kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault
* to wait for IO. Note, gup always bails if it is unable to quickly
* get a page and a fatal signal, i.e. SIGKILL, is pending.
*/
- fault->pfn = __gfn_to_pfn_memslot(slot, fault->gfn, false, true, NULL,
- fault->write, &fault->map_writable,
- &fault->hva);
+ foll.flags |= FOLL_INTERRUPTIBLE;
+ foll.flags &= ~FOLL_NOWAIT;
+ fault->pfn = __kvm_follow_pfn(&foll);
+
+ if (!is_error_noslot_pfn(fault->pfn))
+ goto success;
+
+ return RET_PF_CONTINUE;
+success:
+ fault->hva = foll.hva;
+ fault->map_writable = foll.writable;
return RET_PF_CONTINUE;
}
--
2.41.0.255.g8b1d071c50-goog
On Tue, Jul 04, 2023 at 04:50:49PM +0900, David Stevens wrote:
> From: David Stevens <[email protected]>
>
> Migrate from __gfn_to_pfn_memslot to __kvm_follow_pfn.
>
> Signed-off-by: David Stevens <[email protected]>
> ---
> arch/x86/kvm/mmu/mmu.c | 35 +++++++++++++++++++++++++----------
> 1 file changed, 25 insertions(+), 10 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index ec169f5c7dce..e44ab512c3a1 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -4296,7 +4296,12 @@ void kvm_arch_async_page_ready(struct kvm_vcpu *vcpu, struct kvm_async_pf *work)
> static int __kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
> {
> struct kvm_memory_slot *slot = fault->slot;
> - bool async;
> + struct kvm_follow_pfn foll = {
> + .slot = slot,
> + .gfn = fault->gfn,
> + .flags = FOLL_GET | (fault->write ? FOLL_WRITE : 0),
> + .allow_write_mapping = true,
> + };
>
> /*
> * Retry the page fault if the gfn hit a memslot that is being deleted
> @@ -4325,12 +4330,14 @@ static int __kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault
> return RET_PF_EMULATE;
> }
>
> - async = false;
> - fault->pfn = __gfn_to_pfn_memslot(slot, fault->gfn, false, false, &async,
> - fault->write, &fault->map_writable,
> - &fault->hva);
> - if (!async)
> - return RET_PF_CONTINUE; /* *pfn has correct page already */
> + foll.flags |= FOLL_NOWAIT;
> + fault->pfn = __kvm_follow_pfn(&foll);
> +
> + if (!is_error_noslot_pfn(fault->pfn))
> + goto success;
> +
> + if (fault->pfn != KVM_PFN_ERR_NEEDS_IO)
> + return RET_PF_CONTINUE;
IIUC, FOLL_NOWAIT is set only when we wanna an async fault. So
KVM_PFN_ERR_NEEDS_IO may not be necessary?
B.R.
Yu
On Tue, Jul 04, 2023 at 04:50:49PM +0900,
David Stevens <[email protected]> wrote:
> From: David Stevens <[email protected]>
>
> Migrate from __gfn_to_pfn_memslot to __kvm_follow_pfn.
>
> Signed-off-by: David Stevens <[email protected]>
> ---
> arch/x86/kvm/mmu/mmu.c | 35 +++++++++++++++++++++++++----------
> 1 file changed, 25 insertions(+), 10 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index ec169f5c7dce..e44ab512c3a1 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -4296,7 +4296,12 @@ void kvm_arch_async_page_ready(struct kvm_vcpu *vcpu, struct kvm_async_pf *work)
> static int __kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
> {
> struct kvm_memory_slot *slot = fault->slot;
> - bool async;
> + struct kvm_follow_pfn foll = {
> + .slot = slot,
> + .gfn = fault->gfn,
> + .flags = FOLL_GET | (fault->write ? FOLL_WRITE : 0),
> + .allow_write_mapping = true,
> + };
>
> /*
> * Retry the page fault if the gfn hit a memslot that is being deleted
> @@ -4325,12 +4330,14 @@ static int __kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault
> return RET_PF_EMULATE;
> }
>
> - async = false;
> - fault->pfn = __gfn_to_pfn_memslot(slot, fault->gfn, false, false, &async,
> - fault->write, &fault->map_writable,
> - &fault->hva);
> - if (!async)
> - return RET_PF_CONTINUE; /* *pfn has correct page already */
> + foll.flags |= FOLL_NOWAIT;
> + fault->pfn = __kvm_follow_pfn(&foll);
> +
> + if (!is_error_noslot_pfn(fault->pfn))
We have pfn in struct kvm_follow_pfn as output. Can we make __kvm_follow_pfn()
return int instead of kvm_pfn_t? KVM_PFN_* seems widely used, though.
> + goto success;
> +
> + if (fault->pfn != KVM_PFN_ERR_NEEDS_IO)
> + return RET_PF_CONTINUE;
>
> if (!fault->prefetch && kvm_can_do_async_pf(vcpu)) {
> trace_kvm_try_async_get_page(fault->addr, fault->gfn);
> @@ -4348,9 +4355,17 @@ static int __kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault
> * to wait for IO. Note, gup always bails if it is unable to quickly
> * get a page and a fatal signal, i.e. SIGKILL, is pending.
> */
> - fault->pfn = __gfn_to_pfn_memslot(slot, fault->gfn, false, true, NULL,
> - fault->write, &fault->map_writable,
> - &fault->hva);
> + foll.flags |= FOLL_INTERRUPTIBLE;
> + foll.flags &= ~FOLL_NOWAIT;
> + fault->pfn = __kvm_follow_pfn(&foll);
> +
> + if (!is_error_noslot_pfn(fault->pfn))
> + goto success;
> +
> + return RET_PF_CONTINUE;
> +success:
> + fault->hva = foll.hva;
> + fault->map_writable = foll.writable;
> return RET_PF_CONTINUE;
> }
>
> --
> 2.41.0.255.g8b1d071c50-goog
>
--
Isaku Yamahata <[email protected]>
On Wed, Jul 05, 2023, Yu Zhang wrote:
> On Tue, Jul 04, 2023 at 04:50:49PM +0900, David Stevens wrote:
> > From: David Stevens <[email protected]>
> >
> > Migrate from __gfn_to_pfn_memslot to __kvm_follow_pfn.
Please turn up your changelog verbosity from ~2 to ~8. E.g. explain the transition
from async => FOLL_NOWAIT+KVM_PFN_ERR_NEEDS_IO, there's no reason to force readers
to suss that out on their own.
> > Signed-off-by: David Stevens <[email protected]>
> > ---
> > arch/x86/kvm/mmu/mmu.c | 35 +++++++++++++++++++++++++----------
> > 1 file changed, 25 insertions(+), 10 deletions(-)
> >
> > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> > index ec169f5c7dce..e44ab512c3a1 100644
> > --- a/arch/x86/kvm/mmu/mmu.c
> > +++ b/arch/x86/kvm/mmu/mmu.c
> > @@ -4296,7 +4296,12 @@ void kvm_arch_async_page_ready(struct kvm_vcpu *vcpu, struct kvm_async_pf *work)
> > static int __kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
> > {
> > struct kvm_memory_slot *slot = fault->slot;
> > - bool async;
> > + struct kvm_follow_pfn foll = {
> > + .slot = slot,
> > + .gfn = fault->gfn,
> > + .flags = FOLL_GET | (fault->write ? FOLL_WRITE : 0),
> > + .allow_write_mapping = true,
> > + };
> >
> > /*
> > * Retry the page fault if the gfn hit a memslot that is being deleted
> > @@ -4325,12 +4330,14 @@ static int __kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault
> > return RET_PF_EMULATE;
> > }
> >
> > - async = false;
> > - fault->pfn = __gfn_to_pfn_memslot(slot, fault->gfn, false, false, &async,
> > - fault->write, &fault->map_writable,
> > - &fault->hva);
> > - if (!async)
> > - return RET_PF_CONTINUE; /* *pfn has correct page already */
> > + foll.flags |= FOLL_NOWAIT;
> > + fault->pfn = __kvm_follow_pfn(&foll);
> > +
> > + if (!is_error_noslot_pfn(fault->pfn))
> > + goto success;
> > +
> > + if (fault->pfn != KVM_PFN_ERR_NEEDS_IO)
> > + return RET_PF_CONTINUE;
>
> IIUC, FOLL_NOWAIT is set only when we wanna an async fault. So
> KVM_PFN_ERR_NEEDS_IO may not be necessary?
But FOLL_NOWAIT is set above. This logic is essentially saying "bail immediately
if __gfn_to_pfn_memslot() returned a fatal error".
A commented would definitely be helpful though. How about?
/*
* If __kvm_follow_pfn() failed because I/O is needed to fault in the
* page, then either set up an asynchronous #PF to do the I/O, or if
* doing an async #PF isn't possible, retry __kvm_follow_pfn() with
I/O allowed. All other failures are fatal, i.e. retrying won't help.
*/
if (fault->pfn != KVM_PFN_ERR_NEEDS_IO)
return RET_PF_CONTINUE;