From: Jason Gunthorpe <jgg@ziepe•ca>
To: Joonwon Kang <joonwonkang@google•com>
Cc: kirill.shutemov@linux•intel.com, Alexander.Grest@microsoft•com,
alexander.shishkin@linux•intel.com, amhetre@nvidia•com,
baolu.lu@linux•intel.com, bp@alien8•de,
dave.hansen@linux•intel.com,
easwar.hariharan@linux•microsoft.com, hpa@zytor•com,
iommu@lists•linux.dev, jacob.jun.pan@linux•intel.com,
joro@8bytes•org, jpb@kernel•org, kas@kernel•org, kees@kernel•org,
kevin.tian@intel•com, linux-arm-kernel@lists•infradead.org,
linux-kernel@vger•kernel.org, mingo@redhat•com,
nicolinc@nvidia•com, peterz@infradead•org, praan@google•com,
robin.murphy@arm•com, ryasuoka@redhat•com, smostafa@google•com,
sohil.mehta@intel•com, tglx@kernel•org, will@kernel•org,
x86@kernel•org, xin@zytor•com
Subject: Re: [PATCH] iommu: Allow device driver to use its own PASID space for SVA
Date: Mon, 18 May 2026 14:52:49 -0300 [thread overview]
Message-ID: <20260518175249.GS7702@ziepe.ca> (raw)
In-Reply-To: <20260518090654.730478-1-joonwonkang@google.com>
On Mon, May 18, 2026 at 09:06:54AM +0000, Joonwon Kang wrote:
> > On Fri, May 15, 2026 at 09:46:05AM +0000, Joonwon Kang wrote:
> > > diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
> > > index 0ca3912ecb7f..61e2e52105e5 100644
> > > --- a/arch/x86/kernel/traps.c
> > > +++ b/arch/x86/kernel/traps.c
> > > @@ -864,6 +864,8 @@ static bool try_fixup_enqcmd_gp(void)
> > > return false;
> > >
> > > pasid = mm_get_enqcmd_pasid(current->mm);
> > > + if (pasid == IOMMU_PASID_INVALID)
> > > + return false;
> >
> > If you do this then probably you should get rid of mm_valid_pasid(),
> > mm_get_enqcmd_pasid() already has the NULL check so the two functions
> > are kind of pointless.
> >
> > You also missed the other place calling mm_valid_pasid() that should
> > really be sensitive to this as well:
> >
> > static int prctl_enable_tagged_addr(struct mm_struct *mm, unsigned long nr_bits)
> > {
> > [..]
> > if (mm_valid_pasid(mm) &&
> > !test_bit(MM_CONTEXT_FORCE_TAGGED_SVA, &mm->context.flags))
> > return -EINVAL;
> >
> > Make that removal a prep patch
> >
>
> Thanks for pointing this out. I think mm_valid_pasid() is to check if SVA
> is currently in action while mm_get_enqcmd_pasid() is to get the PASID for
> "ENQCMD instruction execution".
> Since it is now possible with this patch to activate SVA without involving
> EL0(for ENQCMD-like instructions),
I see, this thing about which is about LAM should remain, yes
But all the "EL0" machinery about trapping and enabling ENQCMD should
be moved over to mm_get_enqcmd_pasid() and never call mm_valid_pasid()
Jason
next prev parent reply other threads:[~2026-05-18 17:53 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-15 9:46 [PATCH] iommu: Allow device driver to use its own PASID space for SVA Joonwon Kang
2026-05-15 23:18 ` Jason Gunthorpe
2026-05-18 9:06 ` Joonwon Kang
2026-05-18 17:52 ` Jason Gunthorpe [this message]
2026-05-19 8:11 ` Joonwon Kang
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