Now that there's Hyper-V IOMMU driver, Linux can switch to x2apic mode
when supported by the vcpus.
However, the apic access functions for Hyper-V enlightened apic assume
xapic mode only.
As a result, Linux fails to bring up secondary cpus when run as a guest
in QEMU/KVM with both hv_apic and x2apic enabled.
I didn't manage to make my instance of Hyper-V expose x2apic to the
guest; nor does Hyper-V spec document the expected behavior. However,
a Windows guest running in QEMU/KVM with hv_apic and x2apic and a big
number of vcpus (so that it turns on x2apic mode) does use enlightened
apic MSRs passing unshifted 32bit destination id and falls back to the
regular x2apic MSRs for less frequently used apic fields.
So implement the same behavior, by replacing enlightened apic access
functions (only those where it makes a difference) with their
x2apic-aware versions when x2apic is in use.
Fixes: 29217a474683 ("iommu/hyper-v: Add Hyper-V stub IOMMU driver")
Fixes: 6b48cb5f8347 ("X86/Hyper-V: Enlighten APIC access")
Cc: [email protected]
Signed-off-by: Roman Kagan <[email protected]>
---
arch/x86/hyperv/hv_apic.c | 48 ++++++++++++++++++++++++++++++++++++---
1 file changed, 45 insertions(+), 3 deletions(-)
diff --git a/arch/x86/hyperv/hv_apic.c b/arch/x86/hyperv/hv_apic.c
index 5c056b8aebef..9564fec00375 100644
--- a/arch/x86/hyperv/hv_apic.c
+++ b/arch/x86/hyperv/hv_apic.c
@@ -53,6 +53,11 @@ static void hv_apic_icr_write(u32 low, u32 id)
wrmsrl(HV_X64_MSR_ICR, reg_val);
}
+static void hv_x2apic_icr_write(u32 low, u32 id)
+{
+ wrmsr(HV_X64_MSR_ICR, low, id);
+}
+
static u32 hv_apic_read(u32 reg)
{
u32 reg_val, hi;
@@ -70,6 +75,23 @@ static u32 hv_apic_read(u32 reg)
}
}
+static u32 hv_x2apic_read(u32 reg)
+{
+ u32 reg_val, hi;
+
+ switch (reg) {
+ case APIC_EOI:
+ rdmsr(HV_X64_MSR_EOI, reg_val, hi);
+ return reg_val;
+ case APIC_TASKPRI:
+ rdmsr(HV_X64_MSR_TPR, reg_val, hi);
+ return reg_val;
+
+ default:
+ return native_apic_msr_read(reg);
+ }
+}
+
static void hv_apic_write(u32 reg, u32 val)
{
switch (reg) {
@@ -84,6 +106,20 @@ static void hv_apic_write(u32 reg, u32 val)
}
}
+static void hv_x2apic_write(u32 reg, u32 val)
+{
+ switch (reg) {
+ case APIC_EOI:
+ wrmsr(HV_X64_MSR_EOI, val, 0);
+ break;
+ case APIC_TASKPRI:
+ wrmsr(HV_X64_MSR_TPR, val, 0);
+ break;
+ default:
+ native_apic_msr_write(reg, val);
+ }
+}
+
static void hv_apic_eoi_write(u32 reg, u32 val)
{
struct hv_vp_assist_page *hvp = hv_vp_assist_page[smp_processor_id()];
@@ -262,9 +298,15 @@ void __init hv_apic_init(void)
if (ms_hyperv.hints & HV_X64_APIC_ACCESS_RECOMMENDED) {
pr_info("Hyper-V: Using MSR based APIC access\n");
apic_set_eoi_write(hv_apic_eoi_write);
- apic->read = hv_apic_read;
- apic->write = hv_apic_write;
- apic->icr_write = hv_apic_icr_write;
+ if (x2apic_enabled()) {
+ apic->read = hv_x2apic_read;
+ apic->write = hv_x2apic_write;
+ apic->icr_write = hv_x2apic_icr_write;
+ } else {
+ apic->read = hv_apic_read;
+ apic->write = hv_apic_write;
+ apic->icr_write = hv_apic_icr_write;
+ }
apic->icr_read = hv_apic_icr_read;
}
}
--
2.21.0
Hi Roman,
Thank you for the patch! Yet something to improve:
[auto build test ERROR on tip/x86/core]
[cannot apply to v5.4-rc1 next-20190930]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]
url: https://github.com/0day-ci/linux/commits/Roman-Kagan/x86-hyperv-make-vapic-support-x2apic-mode/20191001-044238
config: x86_64-randconfig-e004-201939 (attached as .config)
compiler: gcc-7 (Debian 7.4.0-13) 7.4.0
reproduce:
# save the attached .config to linux build tree
make ARCH=x86_64
If you fix the issue, kindly add following tag
Reported-by: kbuild test robot <[email protected]>
All errors (new ones prefixed by >>):
arch/x86/hyperv/hv_apic.c: In function 'hv_x2apic_read':
>> arch/x86/hyperv/hv_apic.c:91:10: error: implicit declaration of function 'native_apic_msr_read'; did you mean 'native_apic_icr_read'? [-Werror=implicit-function-declaration]
return native_apic_msr_read(reg);
^~~~~~~~~~~~~~~~~~~~
native_apic_icr_read
arch/x86/hyperv/hv_apic.c: In function 'hv_x2apic_write':
>> arch/x86/hyperv/hv_apic.c:119:3: error: implicit declaration of function 'native_apic_msr_write'; did you mean 'native_apic_icr_write'? [-Werror=implicit-function-declaration]
native_apic_msr_write(reg, val);
^~~~~~~~~~~~~~~~~~~~~
native_apic_icr_write
cc1: some warnings being treated as errors
vim +91 arch/x86/hyperv/hv_apic.c
77
78 static u32 hv_x2apic_read(u32 reg)
79 {
80 u32 reg_val, hi;
81
82 switch (reg) {
83 case APIC_EOI:
84 rdmsr(HV_X64_MSR_EOI, reg_val, hi);
85 return reg_val;
86 case APIC_TASKPRI:
87 rdmsr(HV_X64_MSR_TPR, reg_val, hi);
88 return reg_val;
89
90 default:
> 91 return native_apic_msr_read(reg);
92 }
93 }
94
95 static void hv_apic_write(u32 reg, u32 val)
96 {
97 switch (reg) {
98 case APIC_EOI:
99 wrmsr(HV_X64_MSR_EOI, val, 0);
100 break;
101 case APIC_TASKPRI:
102 wrmsr(HV_X64_MSR_TPR, val, 0);
103 break;
104 default:
105 native_apic_mem_write(reg, val);
106 }
107 }
108
109 static void hv_x2apic_write(u32 reg, u32 val)
110 {
111 switch (reg) {
112 case APIC_EOI:
113 wrmsr(HV_X64_MSR_EOI, val, 0);
114 break;
115 case APIC_TASKPRI:
116 wrmsr(HV_X64_MSR_TPR, val, 0);
117 break;
118 default:
> 119 native_apic_msr_write(reg, val);
120 }
121 }
122
---
0-DAY kernel test infrastructure Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all Intel Corporation
Hi Roman,
Thank you for the patch! Yet something to improve:
[auto build test ERROR on tip/x86/core]
[cannot apply to v5.4-rc1 next-20190930]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]
url: https://github.com/0day-ci/linux/commits/Roman-Kagan/x86-hyperv-make-vapic-support-x2apic-mode/20191001-044238
config: x86_64-randconfig-s0-201939 (attached as .config)
compiler: gcc-5 (Ubuntu 5.5.0-12ubuntu1) 5.5.0 20171010
reproduce:
# save the attached .config to linux build tree
make ARCH=x86_64
If you fix the issue, kindly add following tag
Reported-by: kbuild test robot <[email protected]>
All errors (new ones prefixed by >>):
arch/x86//hyperv/hv_apic.c: In function 'hv_x2apic_read':
>> arch/x86//hyperv/hv_apic.c:91:10: error: implicit declaration of function 'native_apic_msr_read' [-Werror=implicit-function-declaration]
return native_apic_msr_read(reg);
^
arch/x86//hyperv/hv_apic.c: In function 'hv_x2apic_write':
>> arch/x86//hyperv/hv_apic.c:119:3: error: implicit declaration of function 'native_apic_msr_write' [-Werror=implicit-function-declaration]
native_apic_msr_write(reg, val);
^
cc1: some warnings being treated as errors
vim +/native_apic_msr_read +91 arch/x86//hyperv/hv_apic.c
77
78 static u32 hv_x2apic_read(u32 reg)
79 {
80 u32 reg_val, hi;
81
82 switch (reg) {
83 case APIC_EOI:
84 rdmsr(HV_X64_MSR_EOI, reg_val, hi);
85 return reg_val;
86 case APIC_TASKPRI:
87 rdmsr(HV_X64_MSR_TPR, reg_val, hi);
88 return reg_val;
89
90 default:
> 91 return native_apic_msr_read(reg);
92 }
93 }
94
95 static void hv_apic_write(u32 reg, u32 val)
96 {
97 switch (reg) {
98 case APIC_EOI:
99 wrmsr(HV_X64_MSR_EOI, val, 0);
100 break;
101 case APIC_TASKPRI:
102 wrmsr(HV_X64_MSR_TPR, val, 0);
103 break;
104 default:
105 native_apic_mem_write(reg, val);
106 }
107 }
108
109 static void hv_x2apic_write(u32 reg, u32 val)
110 {
111 switch (reg) {
112 case APIC_EOI:
113 wrmsr(HV_X64_MSR_EOI, val, 0);
114 break;
115 case APIC_TASKPRI:
116 wrmsr(HV_X64_MSR_TPR, val, 0);
117 break;
118 default:
> 119 native_apic_msr_write(reg, val);
120 }
121 }
122
---
0-DAY kernel test infrastructure Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all Intel Corporation
On Tue, Oct 01, 2019 at 06:44:08AM +0800, kbuild test robot wrote:
> url: https://github.com/0day-ci/linux/commits/Roman-Kagan/x86-hyperv-make-vapic-support-x2apic-mode/20191001-044238
> config: x86_64-randconfig-e004-201939 (attached as .config)
> compiler: gcc-7 (Debian 7.4.0-13) 7.4.0
> reproduce:
> # save the attached .config to linux build tree
> make ARCH=x86_64
>
> If you fix the issue, kindly add following tag
> Reported-by: kbuild test robot <[email protected]>
>
> All errors (new ones prefixed by >>):
>
> arch/x86/hyperv/hv_apic.c: In function 'hv_x2apic_read':
> >> arch/x86/hyperv/hv_apic.c:91:10: error: implicit declaration of function 'native_apic_msr_read'; did you mean 'native_apic_icr_read'? [-Werror=implicit-function-declaration]
> return native_apic_msr_read(reg);
> ^~~~~~~~~~~~~~~~~~~~
> native_apic_icr_read
> arch/x86/hyperv/hv_apic.c: In function 'hv_x2apic_write':
> >> arch/x86/hyperv/hv_apic.c:119:3: error: implicit declaration of function 'native_apic_msr_write'; did you mean 'native_apic_icr_write'? [-Werror=implicit-function-declaration]
> native_apic_msr_write(reg, val);
> ^~~~~~~~~~~~~~~~~~~~~
> native_apic_icr_write
> cc1: some warnings being treated as errors
Oops, !CONFIG_X86_X2APIC needs to be handled. Will post v2.
Roman.