From: "Thomas Hellström (VMware)" <thomas_os@shipmail.org>
To: Dave Hansen <dave.hansen@intel.com>,
linux-kernel@vger.kernel.org, x86@kernel.org,
pv-drivers@vmware.com
Cc: "Thomas Hellstrom" <thellstrom@vmware.com>,
"Dave Hansen" <dave.hansen@linux.intel.com>,
"Andy Lutomirski" <luto@kernel.org>,
"Peter Zijlstra" <peterz@infradead.org>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Ingo Molnar" <mingo@redhat.com>,
"Borislav Petkov" <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>,
"Christoph Hellwig" <hch@infradead.org>,
"Christian König" <christian.koenig@amd.com>,
"Marek Szyprowski" <m.szyprowski@samsung.com>,
"Tom Lendacky" <thomas.lendacky@amd.com>,
"Shutemov, Kirill" <kirill.shutemov@intel.com>
Subject: Re: [RFC PATCH 1/2] x86: Don't let pgprot_modify() change the page encryption bit
Date: Thu, 5 Sep 2019 18:29:25 +0200 [thread overview]
Message-ID: <1ceb9abc-7a11-eaa1-b286-11647211e2fc@shipmail.org> (raw)
In-Reply-To: <1badd275-91aa-45a6-0a89-ded65c7c3829@intel.com>
On 9/5/19 5:59 PM, Dave Hansen wrote:
> On 9/5/19 8:21 AM, Thomas Hellström (VMware) wrote:
>>>> #define pgprot_modify pgprot_modify
>>>> static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t
>>>> newprot)
>>>> {
>>>> - pgprotval_t preservebits = pgprot_val(oldprot) & _PAGE_CHG_MASK;
>>>> - pgprotval_t addbits = pgprot_val(newprot);
>>>> + pgprotval_t preservebits = pgprot_val(oldprot) &
>>>> + (_PAGE_CHG_MASK | sme_me_mask);
>>>> + pgprotval_t addbits = pgprot_val(newprot) & ~sme_me_mask;
>>>> return __pgprot(preservebits | addbits);
>>>> }
>>> _PAGE_CHG_MASK is claiming similar functionality about preserving bits
>>> when changing PTEs:
> ...
>>>> #define _PAGE_CHG_MASK (PTE_PFN_MASK | _PAGE_PCD | _PAGE_PWT
>>>> | \
>>>> _PAGE_SPECIAL | _PAGE_ACCESSED |
>>>> _PAGE_DIRTY | \
>>>> _PAGE_SOFT_DIRTY | _PAGE_DEVMAP)
>>> This makes me wonder if we should be including sme_me_mask in
>>> _PAGE_CHG_MASK (logically).
>> I was thinking the same. But what confuses me is that addbits isn't
>> masked with ~_PAGE_CHG_MASK, which is needed for sme_me_mask, since the
>> problem otherwise is typically that the encryption bit is incorrectly
>> set in addbits. I wonder whether it's an optimization or intentional.
> I think there's a built-in assumption that 'newprot' won't have any of
> the _PAGE_CHG_MASK bits set. That makes sense because there are no
> protection bits in the mask. But, the code certainly doesn't enforce that.
>
> Are you seeing 'sme_me_mask' bits set in 'newprot'?
Yes. AFAIK it's only one bit, and typically always set.
/Thomas
next prev parent reply other threads:[~2019-09-05 16:29 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-05 10:35 [RFC PATCH 0/2] Fix SEV user-space mapping of unencrypted coherent memory Thomas Hellström (VMware)
2019-09-05 10:35 ` [RFC PATCH 1/2] x86: Don't let pgprot_modify() change the page encryption bit Thomas Hellström (VMware)
2019-09-05 14:15 ` Dave Hansen
2019-09-05 15:21 ` Thomas Hellström (VMware)
2019-09-05 15:24 ` Christoph Hellwig
2019-09-05 16:40 ` Thomas Hellström (VMware)
2019-09-05 17:05 ` dma_mmap_fault discussion Thomas Hellström (VMware)
2019-09-06 6:32 ` Christoph Hellwig
2019-09-06 7:10 ` Thomas Hellström (VMware)
2019-09-06 7:20 ` Christoph Hellwig
2019-09-10 8:37 ` Thomas Hellström (VMware)
2019-09-10 16:11 ` [RFC PATCH 1/2] x86: Don't let pgprot_modify() change the page encryption bit Andy Lutomirski
2019-09-10 19:26 ` Thomas Hellström (VMware)
2019-09-11 4:18 ` Andy Lutomirski
2019-09-11 7:49 ` Thomas Hellström (VMware)
2019-09-11 18:03 ` Andy Lutomirski
2019-09-12 8:29 ` Thomas Hellström (VMware)
2019-09-11 9:08 ` Koenig, Christian
2019-09-11 10:10 ` TTM huge page-faults WAS: " Thomas Hellström (VMware)
2019-09-11 14:06 ` Koenig, Christian
2019-09-11 15:08 ` Thomas Hellström (VMware)
2019-09-24 12:03 ` Koenig, Christian
2019-09-05 15:59 ` Dave Hansen
2019-09-05 16:29 ` Thomas Hellström (VMware) [this message]
2019-09-05 10:35 ` [RFC PATCH 2/2] dma-mapping: Fix dma_pgprot() for unencrypted coherent pages Thomas Hellström (VMware)
2019-09-05 11:23 ` [RFC PATCH 0/2] Fix SEV user-space mapping of unencrypted coherent memory Christoph Hellwig
2019-09-10 6:11 ` Christoph Hellwig
2019-09-10 6:25 ` Thomas Hellström (VMware)
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