From: Vasant Hegde <vashegde@amd.com>
To: Tom Lendacky <thomas.lendacky@amd.com>,
Vasant Hegde <vasant.hegde@amd.com>,
iommu@lists.linux.dev, joro@8bytes.org
Cc: suravee.suthikulpanit@amd.com, bp@alien8.de,
Ashish Kalra <ashish.kalra@amd.com>,
Michael Roth <michael.roth@amd.com>
Subject: Re: [PATCH v2 rc] iommu/amd: Do not enable SNP when V2 page table is enabled
Date: Wed, 10 Apr 2024 09:53:34 +0530 [thread overview]
Message-ID: <7863b2ff-e4f3-464f-8e95-fa3ca0444dbd@amd.com> (raw)
In-Reply-To: <9f2ffe44-80bf-d1dc-239a-f5fbff21b237@amd.com>
Tom,
On 4/9/2024 8:06 PM, Tom Lendacky wrote:
> On 4/9/24 00:13, Vasant Hegde wrote:
>> DTE[Mode]=0 is not supported when SNP is enabled in the host. That means
>> to support SNP, IOMMU must be configured with V1 page table (See IOMMU
>> spec [1] for the details). If user passes kernel command line to
>> configure
>> IOMMU domains with v2 page table (amd_iommu=pgtbl_v2) then disable SNP.
>
> Might be nice to say that you are doing as the user asked by not forcing
> the pagetables to v1.
Sure. I will update the description.
>
> One minor comment below, otherwise:
>
> Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
>
>>
>> [1]
>> https://www.amd.com/content/dam/amd/en/documents/processor-tech-docs/specifications/48882_IOMMU.pdf
>>
>> Cc: Ashish Kalra <ashish.kalra@amd.com>
>> Cc: Michael Roth <michael.roth@amd.com>
>> Cc: Tom Lendacky <thomas.lendacky@amd.com>
>> Signed-off-by: Vasant Hegde <vasant.hegde@amd.com>
>> ---
>> Changes in v2:
>> - Rebased on top of v6.9-rc3 and resolved the conflict.
>>
>> -Vasant
>>
>> drivers/iommu/amd/init.c | 21 +++++++++++----------
>> 1 file changed, 11 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
>> index 005981c2f96a..0d9b69765099 100644
>> --- a/drivers/iommu/amd/init.c
>> +++ b/drivers/iommu/amd/init.c
>> @@ -3215,28 +3215,29 @@ static void iommu_snp_enable(void)
>> return;
>> /*
>> * The SNP support requires that IOMMU must be enabled, and is
>> - * not configured in the passthrough mode.
>> + * configured with V1 page table (DTE[Mode] = 0 is not supported).
>> */
>> if (no_iommu || iommu_default_passthrough()) {
>> pr_err("SNP: IOMMU disabled or configured in passthrough
>> mode, SNP cannot be supported.\n");
>> - cc_platform_clear(CC_ATTR_HOST_SEV_SNP);
>> - return;
>> + goto disable_snp;
>> + }
>> +
>> + if (amd_iommu_pgtable != AMD_IOMMU_V1) {
>> + pr_warn("SNP: IOMMU is configured with V2 page table mode,
>> SNP cannot be supported.\n");
>
> In the previous check, pr_err() is used, while here pr_warn() is used.
> Should be consistent. Not sure if that means changing the pr_err() to
> pr_warn() or making this pr_warn() a pr_err().
Looks like we had this inconsistency from beginning. May be we should
convert it to warning. I will post separate fix for that.
-Vasant
prev parent reply other threads:[~2024-04-10 4:23 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-09 5:13 [PATCH v2 rc] iommu/amd: Do not enable SNP when V2 page table is enabled Vasant Hegde
2024-04-09 14:36 ` Tom Lendacky
2024-04-10 4:23 ` Vasant Hegde [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=7863b2ff-e4f3-464f-8e95-fa3ca0444dbd@amd.com \
--to=vashegde@amd.com \
--cc=ashish.kalra@amd.com \
--cc=bp@alien8.de \
--cc=iommu@lists.linux.dev \
--cc=joro@8bytes.org \
--cc=michael.roth@amd.com \
--cc=suravee.suthikulpanit@amd.com \
--cc=thomas.lendacky@amd.com \
--cc=vasant.hegde@amd.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).