[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <Y5HEAYjUorpZJGl+@zn.tnic>
Date: Thu, 8 Dec 2022 12:01:21 +0100
From: Borislav Petkov <bp@...en8.de>
To: Alexey Kardashevskiy <aik@....com>
Cc: Sean Christopherson <seanjc@...gle.com>, kvm@...r.kernel.org,
x86@...nel.org, linux-kernel@...r.kernel.org,
Venu Busireddy <venu.busireddy@...cle.com>,
Tony Luck <tony.luck@...el.com>,
Tom Lendacky <thomas.lendacky@....com>,
Thomas Gleixner <tglx@...utronix.de>,
Peter Zijlstra <peterz@...radead.org>,
Paolo Bonzini <pbonzini@...hat.com>,
Michael Sterritt <sterritt@...gle.com>,
Michael Roth <michael.roth@....com>,
Mario Limonciello <mario.limonciello@....com>,
Ingo Molnar <mingo@...hat.com>,
Heiko Carstens <hca@...ux.ibm.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Andrew Cooper <andrew.cooper3@...rix.com>,
"Jason A. Donenfeld" <Jason@...c4.com>,
"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH kernel 3/3] x86/sev: Do not handle #VC for DR7 read/write
On Thu, Dec 08, 2022 at 06:14:01PM +1100, Alexey Kardashevskiy wrote:
> Sorry, I am not following. How is moving the bit makes
> SEV_STATUS_TO_FEATURES() not needed?
>
> When I am setting it in VMSA SEV_FEATURES - it is a bit 5.
>
> Inside a SEV VM, it is SEV_STATUS MSR and there it is bit 7. Mentioned
> MSR_AMD64_SEV* are SEV_STATUS MSR bits.
>
> Since the current patch is bad, I'd rather define the bit twice then:
Yes.
> arch/x86/include/asm/msr-index.h:
> #define MSR_AMD64_SEV_FEAT_DEBUG_SWAP BIT_ULL(7)
>
> arch/x86/include/asm/svm.h
> #define SVM_SEV_FEAT_DEBUG_SWAP BIT(5)
>
> as nothing really says that SEV_FEATURES is always going to be
> SEV_STATUS>>2, even though it is now.
>
> Soooo what is acceptable solution here? Thanks,
Right, so since you're testing against sev_status which is a copy of
MSR_AMD64_SEV, then you use bit definitions which are for that MSR as
documented in the respective PPR section for "MSRC001_0131 [SEV Status]
(Core::X86::Msr::SEV_Status)"
When you're setting the VMSA's SEV_FEATURES field, then you need a
different define, ofc.
This also automatically takes care of SEV_FEATURES not being tied to
SEV_STATUS >> 2 forever, as you say.
So yes, do the twice thing.
Thx.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
Powered by blists - more mailing lists