* What is an address translation in powerISA jarogn ?
@ 2018-10-16 17:58 Raz
2018-10-17 0:14 ` Benjamin Herrenschmidt
0 siblings, 1 reply; 2+ messages in thread
From: Raz @ 2018-10-16 17:58 UTC (permalink / raw)
To: linuxppc-dev
Section 5.7.3
"Storage accesses in real, hypervisor real, and virtual real
addressing modes are performed in a manner that depends on the
contents of MSR HV , VPM, VRMASD, HRMOR, RMLS, RMOR (see Chapter 2),
bit 0 of the
effective address (EA0),"
Hello
1. If MSR_IR = 0 and MSR_DR = 0, does it mean that addresses are not
translated by the MMU ?
2. If EA0 is the 63-rd bit of the effective address e address ? Does
this mean that the translation model is
derived from the address ? a non privileged context may access
privileged memory.
thank you
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: What is an address translation in powerISA jarogn ?
2018-10-16 17:58 What is an address translation in powerISA jarogn ? Raz
@ 2018-10-17 0:14 ` Benjamin Herrenschmidt
0 siblings, 0 replies; 2+ messages in thread
From: Benjamin Herrenschmidt @ 2018-10-17 0:14 UTC (permalink / raw)
To: Raz, linuxppc-dev
On Tue, 2018-10-16 at 20:58 +0300, Raz wrote:
> Section 5.7.3
> "Storage accesses in real, hypervisor real, and virtual real
> addressing modes are performed in a manner that depends on the
> contents of MSR HV , VPM, VRMASD, HRMOR, RMLS, RMOR (see Chapter 2),
> bit 0 of the
> effective address (EA0),"
>
> Hello
> 1. If MSR_IR = 0 and MSR_DR = 0, does it mean that addresses are not
> translated by the MMU ?
It depends.
If HV=1 (hypervisor mode), then they are only translated to the extent
that HRMOR is applied if the MSB is 0, and untranslated if the MSB is
1.
If HV=0 (guest mode), then they *are* translated but using a different
mechanism than what's normally used when IR/DR=1. This mechanism
depends on whether you are using the Radix or the Hash MMU, and the top
2 bits are ignored.
With hash MMU, it's using things like VRMASD etc... (RMOR is deprecated
afaik) to lookup a "Virtual real mode" area in the hash table. It's
essentially a mapping of the guest "physical" space to real physical
space. It's usually initialized (and maintained) by the HV but the
guest can extend it using things like H_ENTER afaik.
With the radix MMU, it's the guest physical space as mapped by the 2nd
level page tables maintained by the hypervisor.
> 2. If EA0 is the 63-rd bit of the effective address e address ? Does
> this mean that the translation model is
> derived from the address ? a non privileged context may access
> privileged memory.
Nope.
Cheers,
Ben.
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2018-10-17 0:14 ` Benjamin Herrenschmidt
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