From: Paolo Bonzini <pbonzini@redhat.com>
To: "Wang, Wei W" <wei.w.wang@intel.com>,
"Zhong, Yang" <yang.zhong@intel.com>,
"x86@kernel.org" <x86@kernel.org>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"mingo@redhat.com" <mingo@redhat.com>,
"bp@alien8.de" <bp@alien8.de>,
"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>
Cc: "seanjc@google.com" <seanjc@google.com>,
"Nakajima, Jun" <jun.nakajima@intel.com>,
"Tian, Kevin" <kevin.tian@intel.com>,
"jing2.liu@linux.intel.com" <jing2.liu@linux.intel.com>,
"Liu, Jing2" <jing2.liu@intel.com>,
"Zeng, Guang" <guang.zeng@intel.com>
Subject: Re: [PATCH 16/19] kvm: x86: Introduce KVM_{G|S}ET_XSAVE2 ioctl
Date: Mon, 13 Dec 2021 10:24:08 +0100 [thread overview]
Message-ID: <bdda79b5-79e4-22fd-9af8-ec6e87a412ab@redhat.com> (raw)
In-Reply-To: <86d3c3a5d61649079800a2038370365b@intel.com>
On 12/13/21 09:23, Wang, Wei W wrote:
> On Saturday, December 11, 2021 6:13 AM, Paolo Bonzini wrote:
>>
>> By the way, I think KVM_SET_XSAVE2 is not needed. Instead:
>>
>> - KVM_CHECK_EXTENSION(KVM_CAP_XSAVE2) should return the size of the
>> buffer that is passed to KVM_GET_XSAVE2
>>
>> - KVM_GET_XSAVE2 should fill in the buffer expecting that its size is
>> whatever KVM_CHECK_EXTENSION(KVM_CAP_XSAVE2) passes
>>
>> - KVM_SET_XSAVE can just expect a buffer that is bigger than 4k if the
>> save states recorded in the header point to offsets larger than 4k.
>
> I think one issue is that KVM_SET_XSAVE works with "struct kvm_xsave" (hardcoded 4KB buffer),
> including kvm_vcpu_ioctl_x86_set_xsave. The states obtained via KVM_GET_XSAVE2 will be made
> using "struct kvm_xsave2".
>
> Did you mean that we could add a new code path under KVM_SET_XSAVE to make it work with
> the new "struct kvm_xsave2"?
There is no need for struct kvm_xsave2, because there is no need for a
"size" argument.
- KVM_GET_XSAVE2 *is* needed, and it can expect a buffer as big as the
return value of KVM_CHECK_EXTENSION(KVM_CAP_XSAVE2)
- but KVM_SET_XSAVE2 is not needed, because KVM_SET_XSAVE can use
copy_from_user to read the XSTATE_BV, use it to deduce the size of the
buffer, and use copy_from_user to read the full size of the buffer.
For this to work you can redefine struct kvm_xsave to
struct kvm_xsave {
__u32 region[1024];
/*
* KVM_GET_XSAVE only uses 4096 bytes and only returns
* user save states up to save state 17 (TILECFG).
*
* For KVM_GET_XSAVE2, the total size of region + extra
* must be the size that is communicated by
* KVM_CHECK_EXTENSION(KVM_CAP_XSAVE2).
*
* KVM_SET_XSAVE uses the extra field if the struct was
* returned by KVM_GET_XSAVE2.
*/
__u32 extra[];
}
Paolo
next prev parent reply other threads:[~2021-12-13 9:24 UTC|newest]
Thread overview: 80+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-08 0:03 [PATCH 00/19] AMX Support in KVM Yang Zhong
2021-12-08 0:03 ` [PATCH 01/19] x86/fpu: Extend prctl() with guest permissions Yang Zhong
2021-12-14 0:16 ` Thomas Gleixner
2021-12-08 0:03 ` [PATCH 02/19] x86/fpu: Prepare KVM for dynamically enabled states Yang Zhong
2021-12-13 9:12 ` Paolo Bonzini
2021-12-13 12:00 ` Thomas Gleixner
2021-12-13 12:45 ` Paolo Bonzini
2021-12-13 19:50 ` Thomas Gleixner
2021-12-08 0:03 ` [PATCH 03/19] kvm: x86: Fix xstate_required_size() to follow XSTATE alignment rule Yang Zhong
2021-12-08 0:03 ` [PATCH 04/19] kvm: x86: Check guest xstate permissions when KVM_SET_CPUID2 Yang Zhong
2021-12-08 0:03 ` [PATCH 05/19] x86/fpu: Move xfd initialization out of __fpstate_reset() to the callers Yang Zhong
2021-12-10 22:33 ` Thomas Gleixner
2021-12-08 0:03 ` [PATCH 06/19] x86/fpu: Add reallocation mechanims for KVM Yang Zhong
2021-12-08 0:03 ` [PATCH 07/19] kvm: x86: Propagate fpstate reallocation error to userspace Yang Zhong
2021-12-10 15:44 ` Paolo Bonzini
2021-12-08 0:03 ` [PATCH 08/19] x86/fpu: Move xfd_update_state() to xstate.c and export symbol Yang Zhong
2021-12-10 22:44 ` Thomas Gleixner
2021-12-08 0:03 ` [PATCH 09/19] kvm: x86: Prepare reallocation check Yang Zhong
2021-12-13 9:16 ` Paolo Bonzini
2021-12-14 7:06 ` Tian, Kevin
2021-12-14 10:16 ` Paolo Bonzini
2021-12-14 14:41 ` Liu, Jing2
2021-12-15 7:09 ` Tian, Kevin
2021-12-08 0:03 ` [PATCH 10/19] kvm: x86: Emulate WRMSR of guest IA32_XFD Yang Zhong
2021-12-10 16:02 ` Paolo Bonzini
2021-12-13 7:51 ` Liu, Jing2
2021-12-13 9:01 ` Paolo Bonzini
2021-12-14 10:26 ` Yang Zhong
2021-12-14 11:24 ` Paolo Bonzini
2021-12-10 23:09 ` Thomas Gleixner
2021-12-13 15:06 ` Paolo Bonzini
2021-12-13 19:45 ` Thomas Gleixner
2021-12-13 21:23 ` Thomas Gleixner
2021-12-14 7:16 ` Tian, Kevin
2021-12-08 0:03 ` [PATCH 11/19] kvm: x86: Check fpstate reallocation in XSETBV emulation Yang Zhong
2021-12-08 0:03 ` [PATCH 12/19] x86/fpu: Prepare KVM for bringing XFD state back in-sync Yang Zhong
2021-12-10 23:11 ` Thomas Gleixner
2021-12-08 0:03 ` [PATCH 13/19] kvm: x86: Disable WRMSR interception for IA32_XFD on demand Yang Zhong
2021-12-08 7:23 ` Liu, Jing2
2021-12-08 0:03 ` [PATCH 14/19] x86/fpu: Prepare for KVM XFD_ERR handling Yang Zhong
2021-12-10 16:16 ` Paolo Bonzini
2021-12-10 23:20 ` Thomas Gleixner
2021-12-08 0:03 ` [PATCH 15/19] kvm: x86: Save and restore guest XFD_ERR properly Yang Zhong
2021-12-10 16:23 ` Paolo Bonzini
2021-12-10 22:01 ` Paolo Bonzini
2021-12-12 13:10 ` Yang Zhong
2021-12-11 0:10 ` Thomas Gleixner
2021-12-11 1:31 ` Paolo Bonzini
2021-12-11 3:23 ` Tian, Kevin
2021-12-11 13:10 ` Thomas Gleixner
2021-12-11 3:07 ` Tian, Kevin
2021-12-11 13:29 ` Thomas Gleixner
2021-12-12 1:50 ` Tian, Kevin
2021-12-12 9:10 ` Paolo Bonzini
2021-12-08 0:03 ` [PATCH 16/19] kvm: x86: Introduce KVM_{G|S}ET_XSAVE2 ioctl Yang Zhong
2021-12-10 16:25 ` Paolo Bonzini
2021-12-10 16:30 ` Paolo Bonzini
2021-12-10 22:13 ` Paolo Bonzini
2021-12-13 8:23 ` Wang, Wei W
2021-12-13 9:24 ` Paolo Bonzini [this message]
2021-12-14 6:06 ` Wang, Wei W
2021-12-14 6:18 ` Paolo Bonzini
2021-12-15 2:39 ` Wang, Wei W
2021-12-15 13:42 ` Paolo Bonzini
2021-12-16 8:25 ` Wang, Wei W
2021-12-16 10:28 ` Paolo Bonzini
2021-12-20 17:54 ` State Component 18 and Palette 1 (Re: [PATCH 16/19] kvm: x86: Introduce KVM_{G|S}ET_XSAVE2 ioctl) Nakajima, Jun
2021-12-22 14:44 ` Paolo Bonzini
2021-12-22 23:47 ` Nakajima, Jun
2021-12-22 14:52 ` Dave Hansen
2021-12-22 23:51 ` Nakajima, Jun
2021-12-13 10:10 ` [PATCH 16/19] kvm: x86: Introduce KVM_{G|S}ET_XSAVE2 ioctl Thomas Gleixner
2021-12-13 10:43 ` Paolo Bonzini
2021-12-13 12:40 ` Thomas Gleixner
2021-12-08 0:03 ` [PATCH 17/19] docs: virt: api.rst: Document the new KVM_{G, S}ET_XSAVE2 ioctls Yang Zhong
2021-12-08 0:03 ` [PATCH 18/19] kvm: x86: AMX XCR0 support for guest Yang Zhong
2021-12-10 16:30 ` Paolo Bonzini
2021-12-08 0:03 ` [PATCH 19/19] kvm: x86: Add AMX CPUIDs support Yang Zhong
2021-12-10 21:52 ` Paolo Bonzini
2021-12-11 21:20 ` [PATCH 00/19] AMX Support in KVM Thomas Gleixner
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