Re: [PATCH 4/8] xen: Use the correctly the Xen memory terminologies
From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Date: 2015-07-28 19:14:06
Also in:
linux-arm-kernel, linux-fbdev, linux-scsi, linuxppc-dev, lkml, netdev
On 07/28/2015 11:02 AM, Julien Grall wrote:
Based on include/xen/mm.h [1], Linux is mistakenly using MFN when GFN is meant, I suspect this is because the first support for Xen was for PV. This brough some misimplementation of helpers on ARM and make the developper confused the expected behavior. For instance, with pfn_to_mfn, we expect to get an MFN based on the name. Although, if we look at the implementation on x86, it's returning a GFN. For clarity and avoid new confusion, replace any reference of mfn into gnf in any helpers used by PV drivers.
quoted hunk ↗ jump to hunk
@@ -730,7 +730,7 @@ static void xen_do_pin(unsigned level, unsigned long pfn) struct mmuext_op op; op.cmd = level; - op.arg1.mfn = pfn_to_mfn(pfn); + op.arg1.mfn = pfn_to_gfn(pfn);
This looks slightly odd. It is correct but given that purpose of this series is to make things more clear perhaps we can add another union member (gfn) to mmuext_op.arg1? (Of course, the hypervisor will continue referring to mfn which could still be confusing)
quoted hunk ↗ jump to hunk
xen_extend_mmuext_op(&op); }@@ -1323,7 +1323,7 @@ static void __xen_write_cr3(bool kernel, unsigned long cr3) trace_xen_mmu_write_cr3(kernel, cr3); if (cr3) - mfn = pfn_to_mfn(PFN_DOWN(cr3)); + mfn = pfn_to_gfn(PFN_DOWN(cr3));
Here too. And further down, thoughout this patch. -boris