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Re: [Xen-devel] [PATCH] x86/xen: Remove use of VLAs

On 04/17/2018 12:16 AM, Juergen Gross wrote:
On 16/04/18 15:27, Boris Ostrovsky wrote:
On 04/13/2018 06:11 PM, Laura Abbott wrote:
There's an ongoing effort to remove VLAs[1] from the kernel to eventually
turn on -Wvla. The few VLAs in use have an upper bound based on a size
of 64K. This doesn't produce an excessively large stack so just switch
the upper bound.

[1] https://lkml.org/lkml/2018/3/7/621

Signed-off-by: Laura Abbott <labbott@xxxxxxxxxx>
  arch/x86/xen/enlighten_pv.c | 6 ++----
  1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index c36d23aa6c35..d96a5a535cbb 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -421,8 +421,7 @@ static void xen_load_gdt(const struct desc_ptr *dtr)
        unsigned long va = dtr->address;
        unsigned int size = dtr->size + 1;
-       unsigned pages = DIV_ROUND_UP(size, PAGE_SIZE);

Isn't dtr->size always either GDT_SIZE or 0?

GDT_SIZE - 1 :-)

-       unsigned long frames[pages];
+       unsigned long frames[DIV_ROUND_UP(SZ_64K, PAGE_SIZE)];

So we could just go with one frame and modify the BUG_ON() further below

Do you want to just remove the loop as well since we're never going
to do more than one frame? We end up with net code deletion.



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