linux-kernel - RE: [PATCH net 1/1] hv_netvsc: Fix missed pagebuf entries in netvsc_dma

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Date:   Tue, 31 Jan 2023 17:01:04 +0000
From:   Haiyang Zhang <haiyangz@...rosoft.com>
To:     "Michael Kelley (LINUX)" <mikelley@...rosoft.com>,
        KY Srinivasan <kys@...rosoft.com>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>,
        Dexuan Cui <decui@...rosoft.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: RE: [PATCH net 1/1] hv_netvsc: Fix missed pagebuf entries in
 netvsc_dma_map/unmap()



> -----Original Message-----
> From: Michael Kelley (LINUX) <mikelley@...rosoft.com>
> Sent: Monday, January 30, 2023 10:33 PM
> To: KY Srinivasan <kys@...rosoft.com>; Haiyang Zhang
> <haiyangz@...rosoft.com>; wei.liu@...nel.org; Dexuan Cui
> <decui@...rosoft.com>; davem@...emloft.net; edumazet@...gle.com;
> kuba@...nel.org; pabeni@...hat.com; netdev@...r.kernel.org; linux-
> hyperv@...r.kernel.org; linux-kernel@...r.kernel.org
> Cc: Michael Kelley (LINUX) <mikelley@...rosoft.com>; stable@...r.kernel.org
> Subject: [PATCH net 1/1] hv_netvsc: Fix missed pagebuf entries in
> netvsc_dma_map/unmap()
> 
> netvsc_dma_map() and netvsc_dma_unmap() currently check the cp_partial
> flag and adjust the page_count so that pagebuf entries for the RNDIS
> portion of the message are skipped when it has already been copied into
> a send buffer. But this adjustment has already been made by code in
> netvsc_send(). The duplicate adjustment causes some pagebuf entries to
> not be mapped. In a normal VM, this doesn't break anything because the
> mapping doesn’t change the PFN. But in a Confidential VM,
> dma_map_single() does bounce buffering and provides a different PFN.
> Failing to do the mapping causes the wrong PFN to be passed to Hyper-V,
> and various errors ensue.
> 
> Fix this by removing the duplicate adjustment in netvsc_dma_map() and
> netvsc_dma_unmap().
> 
> Fixes: 846da38de0e8 ("net: netvsc: Add Isolation VM support for netvsc
> driver")
> Cc: stable@...r.kernel.org
> Signed-off-by: Michael Kelley <mikelley@...rosoft.com>

Reviewed-by: Haiyang Zhang <haiyangz@...rosoft.com>

Thanks!