From: Kiryl Shutsemau <kas@kernel.org>
To: "Aneesh Kumar K.V (Arm)" <aneesh.kumar@kernel.org>
Cc: linux-coco@lists.linux.dev, kvmarm@lists.linux.dev,
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Subject: Re: [RFC PATCH v8 02/14] mm: Zero memory during shared memory transitions
Date: Fri, 25 Sep 2026 13:08:50 +0100 [thread overview]
Message-ID: <arZkEugXwCtKHH64@thinkstation> (raw)
In-Reply-To: <20260924100529.1398790-3-aneesh.kumar@kernel.org>
On Thu, Sep 24, 2026 at 03:35:17PM +0530, Aneesh Kumar K.V (Arm) wrote:
> diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
> index f904a636d449..1f1f39082391 100644
> --- a/arch/x86/coco/tdx/tdx.c
> +++ b/arch/x86/coco/tdx/tdx.c
> @@ -978,6 +978,9 @@ static bool tdx_enc_status_changed(unsigned long vaddr, int numpages, bool enc)
> static int tdx_enc_status_change_prepare(unsigned long vaddr, int numpages,
> bool enc)
> {
> + if (!enc)
> + memset((void *)vaddr, 0, (size_t)numpages << PAGE_SHIFT);
> +
> /*
> * Only handle shared->private conversion here.
> * See the comment in tdx_early_init().
This doesn't make sense to me.
On TDX the memset zeroes a page that is about to be dropped.
MapGPA(shared) makes the VMM back the GPA with different memory, and
what the guest reads afterwards through the shared mapping is whatever
the host has there.
--
Kiryl Shutsemau / Kirill A. Shutemov
next prev parent reply other threads:[~2026-09-25 12:09 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-24 10:05 [RFC PATCH v8 00/14] coco: guest: Add a shared-granule allocator for host-shared memory Aneesh Kumar K.V (Arm)
2026-09-24 10:05 ` [RFC PATCH v8 01/14] mm: Add an allocator for CoCo shared memory Aneesh Kumar K.V (Arm)
2026-09-24 10:05 ` [RFC PATCH v8 02/14] mm: Zero memory during shared memory transitions Aneesh Kumar K.V (Arm)
2026-09-25 12:08 ` Kiryl Shutsemau [this message]
2026-09-24 10:05 ` [RFC PATCH v8 03/14] irqchip/gic-v3-its: Resolve the default NUMA node explicitly Aneesh Kumar K.V (Arm)
2026-09-24 10:05 ` [RFC PATCH v8 04/14] irqchip/gic-v3-its: Allocate shared tables using CoCo shared memory allocator Aneesh Kumar K.V (Arm)
2026-09-24 10:05 ` [RFC PATCH v8 05/14] dma-contiguous: Derive shared alignment from DMA attributes Aneesh Kumar K.V (Arm)
2026-09-24 10:05 ` [RFC PATCH v8 06/14] dma-pool: Allocate CoCo atomic pools using CoCo shared memory allocator Aneesh Kumar K.V (Arm)
2026-09-24 10:05 ` [RFC PATCH v8 07/14] dma-direct: Align CoCo shared DMA allocations to the shared granule size Aneesh Kumar K.V (Arm)
2026-09-24 10:05 ` [RFC PATCH v8 08/14] swiotlb: Align shared IO TLB pools " Aneesh Kumar K.V (Arm)
2026-09-24 10:05 ` [RFC PATCH v8 09/14] swiotlb: Reject misaligned restricted DMA pools for CoCo guests Aneesh Kumar K.V (Arm)
2026-09-24 10:05 ` [RFC PATCH v8 10/14] dma-buf: system_heap: Limit scatterlist entries to the buffer size Aneesh Kumar K.V (Arm)
2026-09-24 10:05 ` [RFC PATCH v8 11/14] dma-buf: system_heap: Allocate shared buffers using CoCo shared memory allocator Aneesh Kumar K.V (Arm)
2026-09-24 10:05 ` [RFC PATCH v8 12/14] swiotlb: Make rounded shared pool capacity allocatable Aneesh Kumar K.V (Arm)
2026-09-24 10:05 ` [RFC PATCH v8 13/14] mm: Assert CoCo shared allocations may sleep Aneesh Kumar K.V (Arm)
2026-09-24 10:05 ` [RFC PATCH v8 14/14] irqchip/gic-v3-its: Preallocate VPE L1 tables Aneesh Kumar K.V (Arm)
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