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Re: [PATCH v2 11/18] KVM/MIPS32: Routines to handle specific traps/excep

To: Sanjay Lal <sanjayl@kymasys.com>
Subject: Re: [PATCH v2 11/18] KVM/MIPS32: Routines to handle specific traps/exceptions while executing the guest.
From: Gleb Natapov <gleb@redhat.com>
Date: Mon, 18 Feb 2013 11:44:50 +0200
Cc: kvm@vger.kernel.org, linux-mips@linux-mips.org
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References: <1353551656-23579-1-git-send-email-sanjayl@kymasys.com> <1353551656-23579-12-git-send-email-sanjayl@kymasys.com> <20130206132018.GC7837@redhat.com> <D2EC658F-5271-4221-8141-930E00D3FF84@kymasys.com>
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On Fri, Feb 15, 2013 at 11:10:46AM -0500, Sanjay Lal wrote:
> 
> On Feb 6, 2013, at 8:20 AM, Gleb Natapov wrote:
> 
> > On Wed, Nov 21, 2012 at 06:34:09PM -0800, Sanjay Lal wrote:
> >> +static gpa_t kvm_trap_emul_gva_to_gpa_cb(gva_t gva)
> >> +{
> >> +  gpa_t gpa;
> >> +  uint32_t kseg = KSEGX(gva);
> >> +
> >> +  if ((kseg == CKSEG0) || (kseg == CKSEG1))
> > You seems to be using KVM_GUEST_KSEGX variants on gva in all other
> > places. Why not here?
> 
> This function is invoked to handle 2 scenarios:
> (1) Parse the boot code config tables setup by QEMU's Malta emulation. The 
> pointers in the tables are actual KSEG0 addresses (unmapped, cached) and not 
> Guest KSEG0 addresses.
> 
Where is it called for that purpose? The only place where gva_to_gpa
callback is called is in kvm/kvm_mips_emul.c:kvm_mips_emulate_(store|load)

> (2) Handle I/O accesses by the guest.  On MIPS platforms, I/O device 
> registers are mapped into the KSEG1 address space (unmapped, uncached).  
> Again like (1) these are actual KSEG1 addresses, which cause an exception and 
> are passed onto QEMU for I/O emulation.
> 
So guest KSEG1 registers is mapped to 0xA0000000-0xBFFFFFFF ranges just
like on a host? Can you give corresponding segment names to those ranges

Guest User address space:   0x00000000 -> 0x40000000 (useg?)
Guest Kernel Unmapped:      0x40000000 -> 0x60000000 (kseg0?)
Guest Kernel Mapped:        0x60000000 -> 0x80000000 (?)


--
                        Gleb.

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