From: Borislav Petkov <bp@alien8.de>
To: "Singh, Brijesh" <brijesh.singh@amd.com>,
"Lendacky, Thomas" <Thomas.Lendacky@amd.com>
Cc: lijiang <lijiang@redhat.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"kexec@lists.infradead.org" <kexec@lists.infradead.org>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"mingo@redhat.com" <mingo@redhat.com>,
"x86@kernel.org" <x86@kernel.org>,
"hpa@zytor.com" <hpa@zytor.com>,
"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
"dyoung@redhat.com" <dyoung@redhat.com>,
"bhe@redhat.com" <bhe@redhat.com>
Subject: Re: [PATCH 1/3] kexec: Do not map the kexec area as decrypted when SEV is active
Date: Mon, 25 Mar 2019 18:32:39 +0100 [thread overview]
Message-ID: <20190325173239.GO12016@zn.tnic> (raw)
In-Reply-To: <652b9166-f06e-c210-3c3f-c9e80a97db18@amd.com>
On Mon, Mar 25, 2019 at 05:17:55PM +0000, Singh, Brijesh wrote:
> By default all the memory regions are mapped encrypted. The
> set_memory_{encrypt,decrypt}() is a generic function which can be
> called explicitly to clear/set the encryption mask from the existing
> memory mapping. The mem_encrypt_active() returns true if either SEV or
> SME is active. So the __set_memory_enc_dec() uses the
> memory_encrypt_active() check to ensure that the function is no-op when
> SME/SEV are not active.
>
> Currently, the arch_kexec_post_alloc_pages() unconditionally clear the
> encryption mask from the kexec area. In case of SEV, we should not clear
> the encryption mask.
Brijesh, I know all that.
Please read what I said here at the end:
https://lkml.kernel.org/r/20190324150034.GH23289@zn.tnic
With this change, the code looks like this:
+ if (sme_active())
+ return set_memory_decrypted((unsigned long)vaddr, pages);
now in __set_memory_enc_dec via set_memory_decrypted():
/* Nothing to do if memory encryption is not active */
if (!mem_encrypt_active())
return 0;
so you have:
if (sme_active())
...
if (!mem_encrypt_active())
now maybe this is all clear to you and Tom but I betcha others will get
confused. Probably something like "well, what should be active now, SME,
SEV or memory encryption in general"?
I hope you're catching my drift.
So if you want to *not* decrypt memory in the SEV case, then doing something
like this should make it a bit more clear:
if (sev_active())
return;
return set_memory_decrypted((unsigned long)vaddr, pages);
along with a comment *why* we're checking here.
But actually, I'd prefer if you had separate wrappers which are called
for SME and for SEV.
I'll let Tom chime in too.
--
Regards/Gruss,
Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
next prev parent reply other threads:[~2019-03-25 17:32 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-15 10:32 [PATCH 0/3] Add kdump support for the SEV enabled guest Lianbo Jiang
2019-03-15 10:32 ` [PATCH 1/3] kexec: Do not map the kexec area as decrypted when SEV is active Lianbo Jiang
2019-03-24 15:00 ` Borislav Petkov
2019-03-25 1:58 ` lijiang
2019-03-25 6:37 ` Borislav Petkov
2019-03-25 17:17 ` Singh, Brijesh
2019-03-25 17:32 ` Borislav Petkov [this message]
2019-03-25 18:17 ` Singh, Brijesh
2019-03-25 19:59 ` Lendacky, Thomas
2019-03-26 10:06 ` Boris Petkov
2019-03-26 1:27 ` lijiang
2019-03-15 10:32 ` [PATCH 2/3] kexec: Set the C-bit in the identity map page table " Lianbo Jiang
2019-03-15 10:32 ` [PATCH 3/3] kdump,proc/vmcore: Enable kdumping encrypted memory when SEV was active Lianbo Jiang
2019-03-15 10:42 ` [PATCH 0/3] Add kdump support for the SEV enabled guest lijiang
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