* [PATCH] target/i386: Clear xsave pkru bit when KVM XCR0 not support
@ 2023-05-17 10:55 Yuchen
2023-05-17 17:08 ` Paolo Bonzini
2023-05-17 17:17 ` Dongli Zhang
0 siblings, 2 replies; 5+ messages in thread
From: Yuchen @ 2023-05-17 10:55 UTC (permalink / raw)
To: qemu-devel@nongnu.org
Cc: pbonzini@redhat.com, rth@twiddle.net, ehabkost@redhat.com,
Chengchiwen
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Migrating guest from Intel new CPU (as Gold 6230) to old CPU (as
E5-2650 v4) will pause on the destination host. Because old CPU
not support xsave pkru feature, and KVM KVM_SET_XSAVE ioctl
return EINVAL.
This kernel commit introduces the problem:
ea4d6938d4c0 x86/fpu: Replace KVMs home brewed FPU copy from user
Signed-off-by: YuChen <yu.chen@h3c.com>
---
target/i386/xsave_helper.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/target/i386/xsave_helper.c b/target/i386/xsave_helper.c
index 996e9f3bfe..64e2b969fe 100644
--- a/target/i386/xsave_helper.c
+++ b/target/i386/xsave_helper.c
@@ -6,6 +6,8 @@
#include "cpu.h"
+static bool has_xsave_pkru;
+
void x86_cpu_xsave_all_areas(X86CPU *cpu, void *buf, uint32_t buflen)
{
CPUX86State *env = &cpu->env;
@@ -47,6 +49,9 @@ void x86_cpu_xsave_all_areas(X86CPU *cpu, void *buf, uint32_t buflen)
stq_p(xmm + 8, env->xmm_regs[i].ZMM_Q(1));
}
+ if (!has_xsave_pkru) {
+ env->xstate_bv &= ~XSTATE_PKRU_MASK;
+ }
header->xstate_bv = env->xstate_bv;
e = &x86_ext_save_areas[XSTATE_YMM_BIT];
@@ -181,6 +186,9 @@ void x86_cpu_xrstor_all_areas(X86CPU *cpu, const void *buf, uint32_t buflen)
env->xmm_regs[i].ZMM_Q(1) = ldq_p(xmm + 8);
}
+ if (xsave->header.xstate_bv & XSTATE_PKRU_MASK) {
+ has_xsave_pkru = true;
+ }
env->xstate_bv = header->xstate_bv;
e = &x86_ext_save_areas[XSTATE_YMM_BIT];
--
2.34.1
-------------------------------------------------------------------------------------------------------------------------------------
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^ permalink raw reply related [flat|nested] 5+ messages in thread* Re: [PATCH] target/i386: Clear xsave pkru bit when KVM XCR0 not support
2023-05-17 10:55 [PATCH] target/i386: Clear xsave pkru bit when KVM XCR0 not support Yuchen
@ 2023-05-17 17:08 ` Paolo Bonzini
[not found] ` <6c64f1b84cbf4dd1a75301fc4615f351@h3c.com>
2023-05-17 17:17 ` Dongli Zhang
1 sibling, 1 reply; 5+ messages in thread
From: Paolo Bonzini @ 2023-05-17 17:08 UTC (permalink / raw)
To: Yuchen, qemu-devel@nongnu.org
Cc: rth@twiddle.net, ehabkost@redhat.com, Chengchiwen
On 5/17/23 12:55, Yuchen wrote:
> Migrating guest from Intel new CPU (as Gold 6230) to old CPU (as
> E5-2650 v4) will pause on the destination host. Because old CPU
> not support xsave pkru feature, and KVM KVM_SET_XSAVE ioctl
> return EINVAL.
>
> This kernel commit introduces the problem:
>
> ea4d6938d4c0 x86/fpu: Replace KVMs home brewed FPU copy from user
>
> Signed-off-by: YuChen <yu.chen@h3c.com>
Would this work instead?
diff --git a/target/i386/xsave_helper.c b/target/i386/xsave_helper.c
index 996e9f3bfef5..d3e5edad2ecd 100644
--- a/target/i386/xsave_helper.c
+++ b/target/i386/xsave_helper.c
@@ -47,7 +47,7 @@ void x86_cpu_xsave_all_areas(X86CPU *cpu, void *buf, uint32_t buflen)
stq_p(xmm + 8, env->xmm_regs[i].ZMM_Q(1));
}
- header->xstate_bv = env->xstate_bv;
+ header->xstate_bv = env->xstate_bv & x86_cpu_xsave_xcr0_components(cpu);
e = &x86_ext_save_areas[XSTATE_YMM_BIT];
if (e->size && e->offset) {
Paolo
^ permalink raw reply related [flat|nested] 5+ messages in thread* Re: [PATCH] target/i386: Clear xsave pkru bit when KVM XCR0 not support
2023-05-17 10:55 [PATCH] target/i386: Clear xsave pkru bit when KVM XCR0 not support Yuchen
2023-05-17 17:08 ` Paolo Bonzini
@ 2023-05-17 17:17 ` Dongli Zhang
1 sibling, 0 replies; 5+ messages in thread
From: Dongli Zhang @ 2023-05-17 17:17 UTC (permalink / raw)
To: Yuchen, qemu-devel@nongnu.org
Cc: pbonzini@redhat.com, rth@twiddle.net, ehabkost@redhat.com,
Chengchiwen
Hi Yuchen,
On 5/17/23 03:55, Yuchen wrote:
> Migrating guest from Intel new CPU (as Gold 6230) to old CPU (as
> E5-2650 v4) will pause on the destination host. Because old CPU
> not support xsave pkru feature, and KVM KVM_SET_XSAVE ioctl
> return EINVAL.
>
> This kernel commit introduces the problem:
> ea4d6938d4c0 x86/fpu: Replace KVMs home brewed FPU copy from user
This kernel commit issue should be resolved by the below kernel commit.
x86/kvm/fpu: Limit guest user_xfeatures to supported bits of XCR0
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ad856280ddea3401e1f5060ef20e6de9f6122c76
Since the old target server does not support pkru, I assume the VM's cpu type
should not support pkru. Therefore, the pkru should never be migrated away from
source server.
Dongli Zhang
>
> Signed-off-by: YuChen <yu.chen@h3c.com>
> ---
> target/i386/xsave_helper.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/target/i386/xsave_helper.c b/target/i386/xsave_helper.c
> index 996e9f3bfe..64e2b969fe 100644
> --- a/target/i386/xsave_helper.c
> +++ b/target/i386/xsave_helper.c
> @@ -6,6 +6,8 @@
> #include "cpu.h"
> +static bool has_xsave_pkru;
> +
> void x86_cpu_xsave_all_areas(X86CPU *cpu, void *buf, uint32_t buflen)
> {
> CPUX86State *env = &cpu->env;
> @@ -47,6 +49,9 @@ void x86_cpu_xsave_all_areas(X86CPU *cpu, void *buf, uint32_t buflen)
> stq_p(xmm + 8, env->xmm_regs[i].ZMM_Q(1));
> }
> + if (!has_xsave_pkru) {
> + env->xstate_bv &= ~XSTATE_PKRU_MASK;
> + }
> header->xstate_bv = env->xstate_bv;
> e = &x86_ext_save_areas[XSTATE_YMM_BIT];
> @@ -181,6 +186,9 @@ void x86_cpu_xrstor_all_areas(X86CPU *cpu, const void *buf, uint32_t buflen)
> env->xmm_regs[i].ZMM_Q(1) = ldq_p(xmm + 8);
> }
> + if (xsave->header.xstate_bv & XSTATE_PKRU_MASK) {
> + has_xsave_pkru = true;
> + }
> env->xstate_bv = header->xstate_bv;
> e = &x86_ext_save_areas[XSTATE_YMM_BIT];
> --
> 2.34.1
> -------------------------------------------------------------------------------------------------------------------------------------
> ?????????????????????????????????
> ????????????????????????????????????????
> ????????????????????????????????????????
> ???
> This e-mail and its attachments contain confidential information from New H3C, which is
> intended only for the person or entity whose address is listed above. Any use of the
> information contained herein in any way (including, but not limited to, total or partial
> disclosure, reproduction, or dissemination) by persons other than the intended
> recipient(s) is prohibited. If you receive this e-mail in error, please notify the sender
> by phone or email immediately and delete it!
>
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2023-05-20 6:22 UTC | newest]
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2023-05-17 10:55 [PATCH] target/i386: Clear xsave pkru bit when KVM XCR0 not support Yuchen
2023-05-17 17:08 ` Paolo Bonzini
[not found] ` <6c64f1b84cbf4dd1a75301fc4615f351@h3c.com>
[not found] ` <e7c5d527-2461-332e-638f-38c95ff2602d@redhat.com>
2023-05-20 1:57 ` 回复: 回复: " Yuchen
2023-05-20 6:21 ` Yuchen
2023-05-17 17:17 ` Dongli Zhang
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