From: Joerg Roedel <joro@8bytes.org>
To: Nadav Amit <nadav.amit@gmail.com>
Cc: Nadav Amit <namit@vmware.com>,
iommu@lists.linux-foundation.org, Will Deacon <will@kernel.org>,
Jiajun Cao <caojiajun@vmware.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] iommu/amd: page-specific invalidations for more than one page
Date: Wed, 7 Apr 2021 12:01:07 +0200 [thread overview]
Message-ID: <YG2C42UdIEsWex2L@8bytes.org> (raw)
In-Reply-To: <20210323210619.513069-1-namit@vmware.com>
On Tue, Mar 23, 2021 at 02:06:19PM -0700, Nadav Amit wrote:
> From: Nadav Amit <namit@vmware.com>
>
> Currently, IOMMU invalidations and device-IOTLB invalidations using
> AMD IOMMU fall back to full address-space invalidation if more than a
> single page need to be flushed.
>
> Full flushes are especially inefficient when the IOMMU is virtualized by
> a hypervisor, since it requires the hypervisor to synchronize the entire
> address-space.
>
> AMD IOMMUs allow to provide a mask to perform page-specific
> invalidations for multiple pages that match the address. The mask is
> encoded as part of the address, and the first zero bit in the address
> (in bits [51:12]) indicates the mask size.
>
> Use this hardware feature to perform selective IOMMU and IOTLB flushes.
> Combine the logic between both for better code reuse.
>
> The IOMMU invalidations passed a smoke-test. The device IOTLB
> invalidations are untested.
Have you thoroughly tested this on real hardware? I had a patch-set
doing the same many years ago and it lead to data corruption under load.
Back then it could have been a bug in my code of course, but it made me
cautious about using targeted invalidations.
Regards,
Joerg
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next prev parent reply other threads:[~2021-04-07 10:01 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-23 21:06 [PATCH] iommu/amd: page-specific invalidations for more than one page Nadav Amit
2021-04-07 10:01 ` Joerg Roedel [this message]
2021-04-07 17:57 ` Nadav Amit
2021-04-08 7:18 ` Joerg Roedel
2021-04-08 10:29 ` Nadav Amit
2021-04-08 13:23 ` Joerg Roedel
2021-04-08 15:16 ` Joerg Roedel
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