From: "Xing, Cedric" <cedric.xing@intel.com>
To: Dan Williams <dan.j.williams@intel.com>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
<x86@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>
Cc: <linux-kernel@vger.kernel.org>, <linux-coco@lists.linux.dev>,
"Dionna Amalie Glaze" <dionnaglaze@google.com>,
Guorui Yu <guorui.yu@linux.alibaba.com>,
James Bottomley <James.Bottomley@hansenpartnership.com>,
Dan Middleton <dan.middleton@linux.intel.com>,
Mikko Ylinen <mikko.ylinen@linux.intel.com>,
Sathyanarayanan Kuppuswamy
<sathyanarayanan.kuppuswamy@linux.intel.com>
Subject: Re: [PATCH v3 4/5] x86/tdx: tdx_mcall_get_report0: Return -EBUSY on TDCALL_OPERAND_BUSY error
Date: Fri, 11 Apr 2025 12:37:33 -0500 [thread overview]
Message-ID: <7d1330e3-a0f0-4a4c-a487-46304822e0fd@intel.com> (raw)
In-Reply-To: <67f601e35845f_720529475@dwillia2-xfh.jf.intel.com.notmuch>
On 4/9/2025 12:13 AM, Dan Williams wrote:
> Cedric Xing wrote:
>> Return `-EBUSY` from tdx_mcall_get_report0() when `TDG.MR.REPORT` returns
>> `TDCALL_OPERAND_BUSY`. This enables the caller to retry obtaining a
>> TDREPORT later if another VCPU is extending an RTMR concurrently.
>
> Can this not be prevented by proper locking? Otherwise this type of
> collision sounds like a kernel bug, not something that should escape to
> userspace.
>
Yes, -EBUSY should never happen with proper locking, which however is
implemented in the upper layer.
Similarly, -EINVAL will also indicate a kernel bug but is left for the
upper layer to handle.
> I.e. userspace can not reasonably know when it is safe to retry, so take
> locks to ensure forward progress.
tdx-guest does WARN() on errors. There are no other users of this
function currently. Returning an error, however, will allow different
error handling in the future (e.g., retry instead of WARN on -EBUSY).
next prev parent reply other threads:[~2025-04-11 17:37 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-04-07 18:59 [PATCH v3 0/5] tsm-mr: Unified Measurement Register ABI for TVMs Cedric Xing
2025-04-07 18:59 ` [PATCH v3 1/5] tsm-mr: Add TVM Measurement Register support Cedric Xing
2025-04-09 0:27 ` Dan Williams
2025-04-11 4:01 ` Xing, Cedric
2025-04-07 18:59 ` [PATCH v3 2/5] tsm-mr: Add tsm-mr sample code Cedric Xing
2025-04-09 2:11 ` kernel test robot
2025-04-09 4:26 ` Dan Williams
2025-04-07 18:59 ` [PATCH v3 3/5] x86/tdx: Add tdx_mcall_extend_rtmr() interface Cedric Xing
2025-04-09 5:10 ` Dan Williams
2025-04-11 17:49 ` Xing, Cedric
2025-04-07 18:59 ` [PATCH v3 4/5] x86/tdx: tdx_mcall_get_report0: Return -EBUSY on TDCALL_OPERAND_BUSY error Cedric Xing
2025-04-09 5:13 ` Dan Williams
2025-04-11 17:37 ` Xing, Cedric [this message]
2025-04-07 18:59 ` [PATCH v3 5/5] virt: tdx-guest: Expose TDX MRs as sysfs attributes Cedric Xing
2025-04-08 20:21 ` [PATCH v3 0/5] tsm-mr: Unified Measurement Register ABI for TVMs Dan Williams
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