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[47.54.130.67]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-8ca36086a61sm63262406d6.4.2026.05.18.10.52.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 18 May 2026 10:52:50 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1wP293-0000000DUnE-2ZCv; Mon, 18 May 2026 14:52:49 -0300 Date: Mon, 18 May 2026 14:52:49 -0300 From: Jason Gunthorpe To: Joonwon Kang 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 Message-ID: <20260518175249.GS7702@ziepe.ca> References: <20260515231808.GQ7702@ziepe.ca> <20260518090654.730478-1-joonwonkang@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline 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