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From: Sean Christopherson <seanjc@google.com>
To: Yang Zhong <yang.zhong@intel.com>
Cc: x86@kernel.org, kvm@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
	linux-kselftest@vger.kernel.org, tglx@linutronix.de,
	mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com,
	pbonzini@redhat.com, corbet@lwn.net, shuah@kernel.org,
	jun.nakajima@intel.com, kevin.tian@intel.com,
	jing2.liu@linux.intel.com, jing2.liu@intel.com,
	guang.zeng@intel.com, wei.w.wang@intel.com
Subject: Re: [PATCH v4 03/21] kvm: x86: Fix xstate_required_size() to follow XSTATE alignment rule
Date: Tue, 4 Jan 2022 19:54:10 +0000	[thread overview]
Message-ID: <YdSl4s78kj/U/5Bl@google.com> (raw)
In-Reply-To: <20211229131328.12283-4-yang.zhong@intel.com>

On Wed, Dec 29, 2021, Yang Zhong wrote:
> From: Jing Liu <jing2.liu@intel.com>
> 
> CPUID.0xD.1.EBX enumerates the size of the XSAVE area (in compacted
> format) required by XSAVES. If CPUID.0xD.i.ECX[1] is set for a state
> component (i), this state component should be located on the next
> 64-bytes boundary following the preceding state component in the
> compacted layout.
> 
> Fix xstate_required_size() to follow the alignment rule. AMX is the
> first state component with 64-bytes alignment to catch this bug.
> 
> Signed-off-by: Jing Liu <jing2.liu@intel.com>
> Signed-off-by: Yang Zhong <yang.zhong@intel.com>
> ---
>  arch/x86/kvm/cpuid.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index 07e9215e911d..148003e26cbb 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -42,7 +42,8 @@ static u32 xstate_required_size(u64 xstate_bv, bool compacted)
>  		if (xstate_bv & 0x1) {
>  		        u32 eax, ebx, ecx, edx, offset;
>  		        cpuid_count(0xD, feature_bit, &eax, &ebx, &ecx, &edx);
> -			offset = compacted ? ret : ebx;
> +			/* ECX[1]: 64B alignment in compacted form */
> +			offset = compacted ? ((ecx & 0x2) ? ALIGN(ret, 64) : ret) : ebx;

That is impressively difficult to read.

			if (compacted)
				offset = (ecx & 0x2) ? ALIGN(ret, 64) : ret;
			else
				offset = ebx;

>  			ret = max(ret, offset + eax);
>  		}
>  

  reply	other threads:[~2022-01-04 19:54 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-29 13:13 [PATCH v4 00/21] AMX Support in KVM Yang Zhong
2021-12-29 13:13 ` [PATCH v4 01/21] x86/fpu: Extend fpu_xstate_prctl() with guest permissions Yang Zhong
2021-12-29 13:13 ` [PATCH v4 02/21] x86/fpu: Prepare guest FPU for dynamically enabled FPU features Yang Zhong
2021-12-29 13:13 ` [PATCH v4 03/21] kvm: x86: Fix xstate_required_size() to follow XSTATE alignment rule Yang Zhong
2022-01-04 19:54   ` Sean Christopherson [this message]
2021-12-29 13:13 ` [PATCH v4 04/21] kvm: x86: Exclude unpermitted xfeatures at KVM_GET_SUPPORTED_CPUID Yang Zhong
2021-12-29 13:13 ` [PATCH v4 05/21] x86/fpu: Make XFD initialization in __fpstate_reset() a function argument Yang Zhong
2021-12-29 13:13 ` [PATCH v4 06/21] x86/fpu: Add guest support to xfd_enable_feature() Yang Zhong
2021-12-29 13:13 ` [PATCH v4 07/21] x86/fpu: Provide fpu_update_guest_perm_features() for guest Yang Zhong
2021-12-29 13:13 ` [PATCH v4 08/21] kvm: x86: Check and enable permitted dynamic xfeatures at KVM_SET_CPUID2 Yang Zhong
2021-12-29 16:55   ` Sean Christopherson
2021-12-30  2:28     ` Tian, Kevin
2021-12-29 13:13 ` [PATCH v4 09/21] x86/fpu: Provide fpu_update_guest_xfd() for IA32_XFD emulation Yang Zhong
2021-12-29 13:13 ` [PATCH v4 10/21] kvm: x86: Add emulation for IA32_XFD Yang Zhong
2022-01-04 19:32   ` Sean Christopherson
2022-01-05  0:22     ` Tian, Kevin
2021-12-29 13:13 ` [PATCH v4 11/21] x86/fpu: Prepare xfd_err in struct fpu_guest Yang Zhong
2021-12-29 13:13 ` [PATCH v4 12/21] kvm: x86: Intercept #NM for saving IA32_XFD_ERR Yang Zhong
2022-01-04 20:01   ` Sean Christopherson
2022-01-05  0:27     ` Tian, Kevin
2021-12-29 13:13 ` [PATCH v4 13/21] kvm: x86: Emulate IA32_XFD_ERR for guest Yang Zhong
2021-12-29 13:13 ` [PATCH v4 14/21] kvm: x86: Disable RDMSR interception of IA32_XFD_ERR Yang Zhong
2022-01-04 19:34   ` Sean Christopherson
2022-01-05  0:23     ` Tian, Kevin
2021-12-29 13:13 ` [PATCH v4 15/21] kvm: x86: Add XCR0 support for Intel AMX Yang Zhong
2021-12-29 13:13 ` [PATCH v4 16/21] kvm: x86: Add CPUID " Yang Zhong
2021-12-29 13:13 ` [PATCH v4 17/21] x86/fpu: Add uabi_size to guest_fpu Yang Zhong
2021-12-29 13:13 ` [PATCH v4 18/21] kvm: x86: Add support for getting/setting expanded xstate buffer Yang Zhong
2022-01-04 19:46   ` Sean Christopherson
2022-01-04 20:45     ` Paolo Bonzini
2022-01-05  4:03       ` Tian, Kevin
2021-12-29 13:13 ` [PATCH v4 19/21] kvm: selftests: Add support for KVM_CAP_XSAVE2 Yang Zhong
2021-12-29 13:13 ` [PATCH v4 20/21] x86/fpu: Provide fpu_sync_guest_vmexit_xfd_state() Yang Zhong
2021-12-29 13:13 ` [PATCH v4 21/21] kvm: x86: Disable interception for IA32_XFD on demand Yang Zhong
2021-12-30  8:46 ` [PATCH v4 00/21] AMX Support in KVM Tian, Kevin
2022-01-04 18:36 ` Paolo Bonzini
2022-01-04 18:54   ` Sean Christopherson
2022-01-05  0:10     ` Tian, Kevin

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