From: Jason Gunthorpe <jgg@nvidia.com>
To: Mostafa Saleh <smostafa@google.com>
Cc: Nicolin Chen <nicolinc@nvidia.com>,
will@kernel.org, robin.murphy@arm.com, joro@8bytes.org,
linux-arm-kernel@lists.infradead.org, iommu@lists.linux.dev,
linux-kernel@vger.kernel.org, skolothumtho@nvidia.com,
praan@google.com, xueshuai@linux.alibaba.com
Subject: Re: [PATCH rc v3 1/4] iommu/arm-smmu-v3: Add ignored bits to fix STE update sequence
Date: Tue, 16 Dec 2025 20:23:52 -0400 [thread overview]
Message-ID: <20251217002352.GJ6079@nvidia.com> (raw)
In-Reply-To: <aUHkGCEeu7L5uCMR@google.com>
On Tue, Dec 16, 2025 at 10:58:33PM +0000, Mostafa Saleh wrote:
> for (i = 0; i != NUM_ENTRY_QWORDS; i++) {
> - /*
> - * Ignored is only used for bits that are used by both entries,
> - * otherwise it is sequenced according to the unused entry.
> - */
> - ignored[i] &= target_used[i] & cur_used[i];
> -
It is not functionally the same thing without this..
> And we only clear the bits from cur_used, there is no need to for the
> other mask ignored (ignored[i] &= target_used[i] & cur_used[i])
> - If an ignored bit is not in cur_used it will not impact
> "cur_used[i] &= ~ignored[i]" as it must be already zero
> - If an ignored bit is not in target_used, it doesn't really matter,
> we can ignore it anyway, as it is safe to do so.
That was an earlier version, it was switched away to this so as to be
less of a change though the reasoning is sound.
Jason
next prev parent reply other threads:[~2025-12-17 0:24 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-12-10 2:45 [PATCH rc v3 0/4] : iommu/arm-smmu-v3: Fix hitless STE update in nesting cases Nicolin Chen
2025-12-10 2:45 ` [PATCH rc v3 1/4] iommu/arm-smmu-v3: Add ignored bits to fix STE update sequence Nicolin Chen
2025-12-14 22:32 ` Mostafa Saleh
2025-12-15 20:51 ` Nicolin Chen
2025-12-16 22:49 ` Mostafa Saleh
2025-12-16 0:09 ` Jason Gunthorpe
2025-12-16 20:46 ` Nicolin Chen
2025-12-16 22:58 ` Mostafa Saleh
2025-12-17 0:23 ` Jason Gunthorpe [this message]
2025-12-10 2:45 ` [PATCH rc v3 2/4] iommu/arm-smmu-v3: Ignore STE MEV when computing the " Nicolin Chen
2025-12-10 2:45 ` [PATCH rc v3 3/4] iommu/arm-smmu-v3: Ignore STE EATS " Nicolin Chen
2025-12-10 2:45 ` [PATCH rc v3 4/4] iommu/arm-smmu-v3-test: Add nested s1bypass/s1dssbypass coverage Nicolin Chen
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