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: 846da38d ("net: netvsc: Add Isolation VM support for netvsc driver")
Cc: stable@vger.kernel.org
Signed-off-by: Michael Kelley <mikelley@microsoft.com>
Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
Link: https://lore.kernel.org/r/1675135986-254490-1-git-send-email-mikelley@microsoft.comSigned-off-by: Paolo Abeni <pabeni@redhat.com>